Classic Chassis Kits?

[michaelmoore]

IIRC (and this is from 30 years ago) the frame on my 1974 Sherpa T was pretty light (it was the newer style with the diagonal tube running from the back of the tank down to the swing arm pivot). It also had the light aluminum hubs with the chromed braking surface. You aren't going to get a lot lighter than that. Most 70s trials frames don't have much in the way of tubing in them, and what is there tends to be pretty small OD, so I don't think anyone is going to see huge improvements with a "trick" frame the way you do with something like a Matchless comp single frame. A lot of the weight in the older bikes is in the engines. A B50 or TT500 engine is 90-95 lbf while a 2005 YZ250F modern 4 stroke single engine I have is 54 lbf complete with carb, ignition and levers. A YZ450 is just a few pounds heavier.

As I mentioned above, you don't need 531 or T45 or 4130 to build a frame, but if you are using exposed thin-wall tubes then the stronger tube will help to reduce the amount of denting that takes place when you drop it. And if you build a frame with tubes loaded in bending (as was not uncommon) you may need the extra strength of the 531 etc to keep the frame from bending and staying bent.

The thing is that not only were there a fairly wide variety of aftermarket frames made and sold "in the period" there were also a number of DIY chassis built by enthusiasts. I've tried to collect photos of as many of those types of limited production or one-off frames as I can find on my website. And I still keep running across ones I've never seen before. Just last night I was thumbing through some early Off Road Reviews (Deryk has given me permission to use selected photos since I make a point of attributing the source and photographer) and spotted a Nick Nicholl's photo of fuel-bearing spine-frame Bantam at the 1969 SSDT (with added on tank) that I don't recall seeing before. And then there's the article on the monoshock Goldie scrambler that was 290 lbf with stock BSA wheels and was built and raced in the early 1960s. There's nothing new under the sun.

The UK was an obvious hotbed of DIY stuff. I've got a good collection of MCN/MCW/MCS from the mid-60s forward and there are lots of "readers specials" pictured - MX, trials, grasstrack and RR. The continent is a bit more of a grey area but I've got photos of DIY frames/heavily modified production frames from there too. Here in the USA we didn't have as much of a trials scene but we did have people like Bill Grapevine and his Maverick (and GRM) trials bikes and the guys at PABATCO with their Hodaka specials, and there are certainly lots of MX, roadrace and dirt track aftermarket and DIY frames that were done over here.

I think the important thing is to keep a reasonably period appearance. That means the parts need to look right and be of the style that was found in the time. If you can't see it, don't worry about it because you aren't going to be tearing down engines after a trial to see if someone has carbon-fiber reeds instead of steel reeds.

In any event, the riders are still going to be the limiting factor in the vast majority of cases.

I think more specials would add to the scene. Modern MX and roadrace is pretty boring because everyone is on pretty standard production bikes these days. Maybe you can find a singles or twins racer with a DIY frame to look at, but for the rest you can just take your Yoshimura catalog and go to the showroom and see all the same bikes as at the races.

cheers,

Michael

[Guest majestyman340]

The twinshock thing already seems to be getting a bit out of hand, with people commonly fitting forks from later monoshock bikes, and according to someone I spoke to last week the recent Phil King trial was won on an adapted monoshock bike.

[Guest majestyman340]

IIRC (and this is from 30 years ago) the frame on my 1974 Sherpa T was pretty light (it was the newer style with the diagonal tube running from the back of the tank down to the swing arm pivot). It also had the light aluminum hubs with the chromed braking surface. You aren't going to get a lot lighter than that. Most 70s trials frames don't have much in the way of tubing in them, and what is there tends to be pretty small OD, so I don't think anyone is going to see huge improvements with a "trick" frame the way you do with something like a Matchless comp single frame. A lot of the weight in the older bikes is in the engines. A B50 or TT500 engine is 90-95 lbf while a 2005 YZ250F modern 4 stroke single engine I have is 54 lbf complete with carb, ignition and levers. A YZ450 is just a few pounds heavier.

As I mentioned above, you don't need 531 or T45 or 4130 to build a frame, but if you are using exposed thin-wall tubes then the stronger tube will help to reduce the amount of denting that takes place when you drop it. And if you build a frame with tubes loaded in bending (as was not uncommon) you may need the extra strength of the 531 etc to keep the frame from bending and staying bent.

The thing is that not only were there a fairly wide variety of aftermarket frames made and sold "in the period" there were also a number of DIY chassis built by enthusiasts. I've tried to collect photos of as many of those types of limited production or one-off frames as I can find on my website. And I still keep running across ones I've never seen before. Just last night I was thumbing through some early Off Road Reviews (Deryk has given me permission to use selected photos since I make a point of attributing the source and photographer) and spotted a Nick Nicholl's photo of fuel-bearing spine-frame Bantam at the 1969 SSDT (with added on tank) that I don't recall seeing before. And then there's the article on the monoshock Goldie scrambler that was 290 lbf with stock BSA wheels and was built and raced in the early 1960s. There's nothing new under the sun.

The UK was an obvious hotbed of DIY stuff. I've got a good collection of MCN/MCW/MCS from the mid-60s forward and there are lots of "readers specials" pictured - MX, trials, grasstrack and RR. The continent is a bit more of a grey area but I've got photos of DIY frames/heavily modified production frames from there too. Here in the USA we didn't have as much of a trials scene but we did have people like Bill Grapevine and his Maverick (and GRM) trials bikes and the guys at PABATCO with their Hodaka specials, and there are certainly lots of MX, roadrace and dirt track aftermarket and DIY frames that were done over here.

I think the important thing is to keep a reasonably period appearance. That means the parts need to look right and be of the style that was found in the time. If you can't see it, don't worry about it because you aren't going to be tearing down engines after a trial to see if someone has carbon-fiber reeds instead of steel reeds.

In any event, the riders are still going to be the limiting factor in the vast majority of cases.

I think more specials would add to the scene. Modern MX and roadrace is pretty boring because everyone is on pretty standard production bikes these days. Maybe you can find a singles or twins racer with a DIY frame to look at, but for the rest you can just take your Yoshimura catalog and go to the showroom and see all the same bikes as at the races.

cheers,

Michael

As an experienced frame builder, would you say the advantages of a high spec tube set for a trials chassis, are more important than the reduced cost of using the cheaper materials, that are favoured by all mainstream manufacturers?

[woody]

The twinshock thing already seems to be getting a bit out of hand, with people commonly fitting forks from later monoshock bikes, and according to someone I spoke to last week the recent Phil King trial was won on an adapted monoshock bike.

Can't see that fitting forks from a TY Mono to a Majesty is a problem as they are no better than a pair of Marzocchis off a 240 Fantic and both were available when Majesties were being ridden. Yam Mono was competing against twinshocks as it was out a good 12 months before other monos. A pair of modern GasGas or Sherco forks is a different matter.

The bike that Chris Koch won the Phil King on is not a converted monoshock Yam. It is a one-off frame built by Jon Bliss with a Yam mono engine fitted. This is what I mean about building your own twinshock lightweight chassis - where is it going to end.

[Guest majestyman340]

Can't see that fitting forks from a TY Mono to a Majesty is a problem as they are no better than a pair of Marzocchis off a 240 Fantic and both were available when Majesties were being ridden. Yam Mono was competing against twinshocks as it was out a good 12 months before other monos. A pair of modern GasGas or Sherco forks is a different matter.

The bike that Chris Koch won the Phil King on is not a converted monoshock Yam. It is a one-off frame built by Jon Bliss with a Yam mono engine fitted. This is what I mean about building your own twinshock lightweight chassis - where is it going to end.

In real terms once anyone fits non-standard forks monoshock forks in a twinshock, there doesnt seem to me a lot of difference whether they are from a Yam Mono or a Rev 3.....................as soon as this sort of thing starts, it wont be long before the later more effective forks are going to start being used.

Not seen the Yam mono engined bike myself, but would suppose that if its ok, then it wont be long before someone turns up with a watercooled motor fitted to a twinshock chassis of some sort? Looking at the ACU handbook the only proviso is chassis must be original twinshock, so something like a Fantic section motor bolted into a 240 frame, would be quite eligible.

[paioli]

does that mean we can finally fit a disc conversion on the front like the early ty mono's !

[michaelmoore]

Cheetah (Gollner?) seems to have offered a disc brake on a trials bike in the late 60s from articles I've seen. It was a heavy car disc brake, but it was a disc brake. And I've seen Campy mechanical discs on early 70's trials specials. I don't see anything wrong with period parts or reasonably accurate replicas of them. Putting a 6 piston caliper and 320mm floating carbon rotor on your G50 Metisse that came with a Rickman disc on the front is pretty obviously getting out of the period.

You can fit Race Tech cartridge emulators to the Ceriani/Betor/Telesco etc 35mm damper rod forks and that's invisible from the outside. There are people who supply conversions to slip late model sportbike cartridges in your Roadholders (I think I've seen photos of some P65 bikes with long Roadholders on them), and again that's (AFAIK) invisible to the viewer.

If someone shows up with something obviously way out of the period it should be pretty easy to spot that and ask them to fix it before the next event.

There is always going to be someone who is going to go past the point where it looks like diminishing returns have set in. If they can do that and have it look acceptable, more power to them. The thing is, the vast majority of people probably have 5 year old fork oil in their bikes (or at least they think they put some in 5 years ago) and whatever springs came in the forks which may or may not be vaguely close to what they need for their weight.

And even if I build something I think is cool (and looks period) that is a significant improvement, I'm still going to be collecting points and falling off on the Novice line and having good riders on stock TL125s do better when the scores are tallied at the end of the day.

Isn't fun supposed to be the goal? There's always going to be someone better or worse than you are so try to find someone about your level and have some friendly competition to see who is the best lower-midpack Novice rider on a given day. For me fiddling with the bike is part of the fun. I changed out parts and modified things when I was riding in the period and I intend to do similar types of things to the bikes now.

I've known some fast racers who had the "if I don't think I have a chance of winning I won't come out" attitude. A lot of those people I haven't seen for a long time because they could no longer win so they stopped riding. That's their choice but it seems kind of sad.

If someone wants to spend a fortune to win an amateur vintage trials championship, that championship and a couple of dollars may be enough to buy them a cup of coffee at the local shop where the barista asks "is that a Harley in your truck?" If that's they way they want to spend their money, as long as they can do it within the rules (and hopefully within the spirit as well as the letter of the rules) I'm all for that. Maybe they'll spend money on something that looks like something I can copy in my shop and use on my bike.

AHRMA Modern Classic is the period of bike that interests me. 7" and 4" suspension limits eliminates a lot of the incentive to chop up a seat subframe to increase rear travel, because that just makes you illegal. Build your own frame? Why not? You can run a stock RL250 Suzuki or you can buy a period Beamish Suzuki and have something that is probably as light as you might build at home. Not everyone can afford to buy in a trick period or replica frame but they may have some knowledge and a torch and the minimal tooling you need to build a frame. If whatever they build can pass the "where'd you get that? Oh, I found it in a barn. Cool, I remember seeing something like that back in 1973 . . ." test it looks period enough to be good to be in the event.

Maybe the twinshock class has issues that can't be as easily dealt with as Modern Classic does. I don't know as I haven't had a chance to get familiar with what is going on in that area.

majestyman340, the tubing is the cheapest part of the frame. You may spend more money on fork and swing arm pivot bearings than you do on steel, and you'll spend way more than either of those in time building the thing (presuming you put a real-world valuation on your time). If your application doesn't need the extra strength of 531 or 4130, why spend the extra money on it? I've learned to start trimming the long sections of tube first so when you cut it too short you can hopefully have it be long enough to use on the next shorter tube instead of having to consider it scrap. I'd rather toss inexpensive scrap in the bucket than expensive scrap.

cheers,

Michael

Edited March 2, 2008 by MichaelMoore

[Guest majestyman340]

Cheetah (Gollner?) seems to have offered a disc brake on a trials bike in the late 60s from articles I've seen. It was a heavy car disc brake, but it was a disc brake. And I've seen Campy mechanical discs on early 70's trials specials. I don't see anything wrong with period parts or reasonably accurate replicas of them. Putting a 6 piston caliper and 320mm floating carbon rotor on your G50 Metisse that came with a Rickman disc on the front is pretty obviously getting out of the period.

You can fit Race Tech cartridge emulators to the Ceriani/Betor/Telesco etc 35mm damper rod forks and that's invisible from the outside. There are people who supply conversions to slip late model sportbike cartridges in your Roadholders (I think I've seen photos of some P65 bikes with long Roadholders on them), and again that's (AFAIK) invisible to the viewer.

If someone shows up with something obviously way out of the period it should be pretty easy to spot that and ask them to fix it before the next event.

There is always going to be someone who is going to go past the point where it looks like diminishing returns have set in. If they can do that and have it look acceptable, more power to them. The thing is, the vast majority of people probably have 5 year old fork oil in their bikes (or at least they think they put some in 5 years ago) and whatever springs came in the forks which may or may not be vaguely close to what they need for their weight.

And even if I build something I think is cool (and looks period) that is a significant improvement, I'm still going to be collecting points and falling off on the Novice line and having good riders on stock TL125s do better when the scores are tallied at the end of the day.

Isn't fun supposed to be the goal? There's always going to be someone better or worse than you are so try to find someone about your level and have some friendly competition to see who is the best lower-midpack Novice rider on a given day. For me fiddling with the bike is part of the fun. I changed out parts and modified things when I was riding in the period and I intend to do similar types of things to the bikes now.

I've known some fast racers who had the "if I don't think I have a chance of winning I won't come out" attitude. A lot of those people I haven't seen for a long time because they could no longer win so they stopped riding. That's their choice but it seems kind of sad.

If someone wants to spend a fortune to win an amateur vintage trials championship, that championship and a couple of dollars may be enough to buy them a cup of coffee at the local shop where the barista asks "is that a Harley in your truck?" If that's they way they want to spend their money, as long as they can do it within the rules (and hopefully within the spirit as well as the letter of the rules) I'm all for that. Maybe they'll spend money on something that looks like something I can copy in my shop and use on my bike.

AHRMA Modern Classic is the period of bike that interests me. 7" and 4" suspension limits eliminates a lot of the incentive to chop up a seat subframe to increase rear travel, because that just makes you illegal. Build your own frame? Why not? You can run a stock RL250 Suzuki or you can buy a period Beamish Suzuki and have something that is probably as light as you might build at home. Not everyone can afford to buy in a trick period or replica frame but they may have some knowledge and a torch and the minimal tooling you need to build a frame. If whatever they build can pass the "where'd you get that? Oh, I found it in a barn. Cool, I remember seeing something like that back in 1973 . . ." test it looks period enough to be good to be in the event.

Maybe the twinshock class has issues that can't be as easily dealt with as Modern Classic does. I don't know as I haven't had a chance to get familiar with what is going on in that area.

majestyman340, the tubing is the cheapest part of the frame. You may spend more money on fork and swing arm pivot bearings than you do on steel, and you'll spend way more than either of those in time building the thing (presuming you put a real-world valuation on your time). If your application doesn't need the extra strength of 531 or 4130, why spend the extra money on it? I've learned to start trimming the long sections of tube first so when you cut it too short you can hopefully have it be long enough to use on the next shorter tube instead of having to consider it scrap. I'd rather toss inexpensive scrap in the bucket than expensive scrap.

cheers,

Michael

I think the Gollner bike used a mechanical disc, which very likely wasnt a lot better than a drum brake of the time. Anyone wanting a drum brake set up that works as well as a disc, should have a look at Martin Willmore's B40, which has a very trick looking TLS drum fitted.

Obviously with all those trick suspension options available to classic trials riders in the US, I would imagine events must be pretty difficult, and would be interested in how an AHRMA national event might compare to a similiar level event here in the UK?

[andy m]

I saw a Gollner TLR mono conversion at Malvern, 200 or 250 not sure. Anyway what if you came across one of these and converted it to twinshock, who would you be upsetting then......... just a thought. Would you be going back to what it was or converting a A/C mono to twinshock.

PS do a search " todays classics" and you will find the Bliss t shock or a similar one in the photos on the subject by Motomerlin.

Edited March 3, 2008 by bo drinker

[michaelmoore]

Obviously with all those trick suspension options available to classic trials riders in the US, I would imagine events must be pretty difficult, and would be interested in how an AHRMA national event might compare to a similiar level event here in the UK?

I think you can get Roadholders converted to modern cartridges by Ron Williams at Maxton and several other sources in the UK, as well as by people in Aus/NZ. I'd be surprised if Racetech's cartridge emulators and other products were not being sold in the UK by someone. In any event, in this modern world buying in from half-way around the world is not uncommon. But the things I mentioned don't seem any fancier than what I read is happening in the UK vintage trials suspension scene so I don't expect that US sections are more difficult than what you get to ride. But then since I only ride the novice line I'm not the one to comment on how the expert lines might compare.

A TLS is going to be less effective if you are trying to stop from hurtling backwards down a slope. Of course, by then you've already got a five, but it still would be nice to have a brake that worked in both directions. Making sure the drum is round and you have good linings that are arced in to the drum makes a lot of difference on most brakees. The small conical Yamaha front brake as was used on the DT2MX and many later bikes stops very well (I put one on my 125 Maico to replace the full-width drum it came with), is fairly light, and pretty common. If it works fine for MX it would seem to be plenty strong enough for trials use.

cheers,

Michael

[frenchie]

Fitting mono Yamaha forks to a majesty is in my opinion just a sensible upgrade to bring the bike in line with the last of the twinshock models that had these type of forks and brake fitted as standard, and most people riding majestys would stop there in the interchange of mono and twinshock parts . To the purest this may be contary to what twinshock trials is about , but to someone one looking to level the playing field its considered to be fair and reasonable. Again and this point has been laboured and discussed over the last weeks where do you draw the line. A mono yamaha engine in whatever frame is contary to the spirit of the twinshock idea, its a blatant atempt to gain advantage and pushes the morals to the extremes of what is acceptable. Most people out there know now where the limits are and clubs actively organising twinshock trials and to a certain extend riders should make this known. Modifications should welcomed and endorsed , but should be keep solely in the spirit of what twinshock trials is about. Not everybody knows what is allowed....but everybody knows whats taking the michael...........

Salut

[tony283]

Majestyman340,

Our rules are a lot more lenient see my recent article on my blog "The Pre 65 Debate". With regard to our pre 65 classes then you may use any item up to model year 1974. That means you don't have to go to enormous expense to find a pair of Betors or Ceris to fit your Triumph or old BSA. Rear shocks as Michael said are limited to 4" travel and this is normally done with a little insert around the shaft. Miller framed Cubs are OK with oil in the top tube but Otter or Faber frames are not allowed in the Premier(pre 65) Classes and must be ridden in Modern Classic. Likewise if you wished to put the old Spanish Onion engine in a TY175 frame again you would be in Modern Classic.

With regard to AHRMA sections we have 4 lines to cater for the 3 rider levels, (Exp/Int/Nov). Mod Class ride 1,2,3, lines and beginners (all classes ride the 4 line. The Prem Class ride Exp on 2, Int on 3/2 (dependant on severity), and Nov on 3.

How do these sections compare ? The 1 line (only used by Mod Class Exp) about = Open to centre Trials of the 1970's

The 2 line Prem Exp Classes and Mod Class Int =Open to centre Trials of the 1960's

The 3 line Novices =Open to Centre Novice Only Trials 60/70's

Hope that helps

Tony

[michaelmoore]

I'll mention that there may be some variance in difficulty depending on what part of the country you are in. A friend of mine (348 Cota) who rides about as well (or poorly) as I do on the 3 line moved from the SF Bay area to the east coast (Philadelphia PA). He said that the 3 line there seemed more like the 2 lines out here, and he really struggled with them.

cheers,

Michael

[paioli]

So what we saying here is , if you own a MAJESTY you can fit mono wheels/yokes/forks/swing arm

because its PERIOD/IN THE SPIRIT and the purest don't matter because these are the RULES in our opinion!

well guys until any RULES are set in stone its time to wake up and smell the coffee, stop winging about it and

campaign for some better RULES, but don't be disappointed if fitting mono parts gets outlawed, hope you kept

hold of all your old majesty bits !

The COTSWOLD ridden by Chris Koch was manufactured as a twinshock, a one off with a air-cooled yamaha

donor engine

[Guest majestyman340]

Fitting mono Yamaha forks to a majesty is in my opinion just a sensible upgrade to bring the bike in line with the last of the twinshock models that had these type of forks and brake fitted as standard, and most people riding majestys would stop there in the interchange of mono and twinshock parts . To the purest this may be contary to what twinshock trials is about , but to someone one looking to level the playing field its considered to be fair and reasonable. Again and this point has been laboured and discussed over the last weeks where do you draw the line. A mono yamaha engine in whatever frame is contary to the spirit of the twinshock idea, its a blatant atempt to gain advantage and pushes the morals to the extremes of what is acceptable. Most people out there know now where the limits are and clubs actively organising twinshock trials and to a certain extend riders should make this known. Modifications should welcomed and endorsed , but should be keep solely in the spirit of what twinshock trials is about. Not everybody knows what is allowed....but everybody knows whats taking the michael...........

Salut

We already have several riders using monshock forks in t/s bikes here in the UK, and the first t/s championship round was won on what seems to be an ultra trick Yamaha mono engined creation, that apparently has a one off custom built chassis!

The point here is that once this sort of thing starts, its not going to be long before t/s is ruined in the same way as P65, with