michaelmoore

It seems like what you can do depends on if you want to run Premier Ltwt or Modern Classic. You could stick the engine in a late model Sherpa T chassis and be legal for MC, but not for PL. Anything you do for PL is automagically legal for MC. An electronic ignition would be high on my recommendations, but then I imported and sold Lucas Ritas for about 14 years so I tend to have an opinion about the OEM points/advancers. Mainly, on engines I tend to go for reliability modifications first and deal with performance after that. Luckily, trials is not as demanding as DT/RR/MX on having a "killer" motor. A reliable motor that is stock other than a good carb and ignition (as Tony recommends) with maybe a little more flywheel mass would seem to get you in the ballpark. Shoot to be as good as a stock TL125 Honda. You don't have to aim very high that way . If you are a good rider you should then be able to do well on the 3 line. http://www.achnasheen.uk.com/tigercub.htm has a modified Cub and http://www.cubsite.com/Cubs.htm has a forum for Cubs. cheers, Michael

A Cub can be entered in Premier Lightweight which is a Pre65 class. "Modifications and major components are limited to those of the era, typical of machines in the 1960's." If you enter in Modern Classic you are good up to and including model year 1979. "Modifications and major components are limited to those of the era, typical of machines of the mid-70's." http://www.ahrma.org/rulebook/08_handbook.pdf for the current rule book. cheers, Michael

On open megaphones my "CR216" that I designed and built was measured by my local race club at about 130dB. That's pretty uncomfortable to be around in the pits but sounds good out on the track. This photo was at Laguna Seca before I installed the fairing. cheers, Michael

Dave, I've noticed that the threads here with a lot of photos (especially where people have "quoted" the original post with the photos several times) take a bit of time to load even with DSL so I thought I'd avoid loading 8 images and slowing things down for others. And anyone who wants to see them can easily click on the links. Old-fashioned Internet courtesy habits can be difficult to break. cheers, Michael

Not exactly an early 1960s 125cc Benly twin, but here are some later 60's CB160/175 twin specials from my website. The first two are in the vintage dirtbike/trials photos: "After two seasons running a 90cc Honda trials special, English dealer Ken Ives built a CD175 engined CB160 trials bike. Low compression, lower gearing, upgraded forks, trials spec wheel diameters and tires made a nice trials bike. Photos from 07 Feb 68 Motor Cycle." http://www.eurospares.com/hon175t1.jpg http://www.eurospares.com/hon175t2.jpg From a page devoted to 160 trials bikes ( http://www.eurospares.com/cb160t.htm ): A special that appeared in a 1969 magazine: Mr. Deeter had overbored the engine to 180ccs, and fitted a single carb head from a 175 Honda. The compression was lowered (method not specified), a milder cam from a Honda CA was inserted, and a brass flywheel fitted to the back of the alternator rotor where the electric starter sprag clutch would normally go. He also built a 2-1 high pipe with fairly short head pipes and a very long tail pipe. The bike was lightened with an aluminum fuel tank from a Van Tech frame kit and Akront alloy rims (19" front/18" rear). A small hub from a Honda S90 was used in the front wheel, and attached to forks from a CL160. The bike was reported to weigh 215 pounds, and Mr. Deeter figured he had a year of part-time labor and $1000 invested in the project. http://www.eurospares.com/deeter.jpg As far as I've gotten with my CB160 Premier Lightweight special inspired by the above bikes: http://www.eurospares.com/160a.jpg http://www.eurospares.com/160b.jpg http://www.eurospares.com/160pipes.jpg I've grafted an 160 alternator (internal) rotor hub into an (external) alternator rotor from an EX250 Kawasaki Ninja to increase flywheel mass. The ports have been filled on both sides http://www.eurospares.com/160ports.jpg Dished XR100 pistons: http://www.eurospares.com/160pist.jpg cheers, Michael

How much extra travel do the new bikes have? A new Scorpa is shown on RYP as 165mm rear which is 6.5" or 2.5 more than vintage allows and front travel of 177mm/6.96" which is the same as many vintage bikes. 315mm/12.4" is the ground clearance. That's about the same ground clearance (or less) than my KT seems to have. While rear travel on the Scorpa is +50% over the KT250, 4" to 6.5" is not quite the same as going from 4" to 12" as VMX did. RYP doesn't give foot peg height for that bike. I didn't spot a nice full-side view type of photo to see where the footpeg height was compared to the bash plate. I don't think we want to have the footpegs lower than the bash plate level. It seems like having them as low as possible with that constraining point would be good. If that is the case, then the modern bikes would be shooting for a similar point as a vintage mount. If modern bikes can get away with 12.4" of ground clearance (which with their somewhat greater rear travel may mean the minimum GC is actually lower than a vintage bike) then perhaps there is no reason to go beyond about 12" on a 7"F/4"R vintage bike. And since the vintage bikes aren't going to be seeing modern obstacles, maybe 10-11" is all that is really needed, and the engine/rider can be lowered that much. cheers, Michael

This didn't seem obviously vintage/twin-shock/modern so I'm posting it in the general section. In another thread Tony Down said about footpeg location "from my own personal preferences I have found the ideal to be 37.5 inches from from wheel spindle to center of rest and 12 inches high." "12 inches high" would seem to presume that the footpegs are not hanging below the engine/bash plate. I'm presuming the footpegs on Tony's bikes are about 1" deep so that would imply an 11" ground clearance. I've seen a number of posts where people have commented that a particular bike had the footrests too high, as in 14, 15" or so. The center of gravity is going to be affected by jacking the engine up quite differently if you are looking at a modern 4T (YZF Yamaha 250 engine is 54.5 lbf with levers, carb and ignition), vintage 2T (my KT250 is 10 lbf more than that) or period thumper (a B50/TT500 etc are in the 90-95lbf range and my G80CS Matchy seems quite a lump). Does clubman trials, even with modern bikes, really need more than about 11" of ground clearance? Jack the engine up, jack the footpegs up to match, raise the rider. And in my case the rider with full gear is an easy 200 lbf which seems like it would make a pretty substantial change vs raising a 55 or 65 lbf engine up an inch. A sideview photo of my stock but for somewhat longer rear dampers KT250 http://www.eurospares.com/graphics/trials/...tsideview1a.jpg shows the engine above a line drawn through the axles, which should be about 13" or so based on the unmounted new Michelins I've got in the garage (presuming they are actually round and not greatly flattened at the contact patch when installed but without a rider). The stock-position footpegs are probably 1.5" above that line. If you've got a taller obstacle, don't you just wheelie a little higher and hold the front wheel up a little longer before/while hitting it so you don't high-center? I can recall reading "back in the day" negative comments about "top hamper" and that makes sense to me. Trials bikes can obviously benefit from a certain minimum ground clearance, but when does it get excessive? Since I've just cut the bottom out of the KT frame I may as well reposition the pegs too. Making them as low as possible seems worthwhile. Lowering the engine and the pegs another inch or two might also be worthwhile. Once the welder is on, why hold back? cheers, Michael

Hi Dave, Yes, that's Charlie's bike. He's a good rider, and raced a KR750 Harley "back in the day" that he'd bought new. The bike has had a lot of of modification done to it. cheers, Michael

The obviious answer is "Orange County Observed Trials". We can have have Junior deraking his bike by cutting the steering head partially off with a cutting torch and then running it into a brick wall (but forgetting to weld it back up afterwards) and Dad will be the observer and will shout abuse and throw pinecones and stones at Junior as he attempts to ride through a section. cheers, Michael

Break the rough ones and not the nice examples. That's why I like to have project bikes. I can get something inexpensive that isn't far from being scrapped and have no qualms about cutting/welding on it. No matter what you do, you've saved it from the scrap yard. But if you've got a nice original bike I can't see breaking it up just so someone else can use the parts to make a nice original bike. cheers, Michael

No, Oilite isn't as sturdy as SAE 660 bearing bronze as it is porus to hold the oil, so it should be saved for light duty stuff. I've got the 660 on hand too. Some plastics are neat materials, but you need to have a good idea of when to use the different ones. Delrin/acetal is probably a good choice for something like rear set lever pivots (or use the Oilite). Teflon is not a good choice as it has problems with cold flow when under pressure. If you run the 660 bronze on a hardened and hard-chromed shaft and get it some grease now and then it will last a very very long time, especially if you can have a pretty good amount of surface area. cheers, Michael

Hi Dave, When I get a press I'm going to go for 20 ton minimum, as a friend occasionally runs into a crankshaft with a lot of interference that will have his 20T press straining. It will do it, but you know it is working pretty hard. Finding space for it in the garage will be the issue. If you use a small drill you can get most of the rubber removed between the outer housing and the center bush of the silentbloc, and the center will then easily press out with a vise. A little bit of careful grinding split the housings and they are now out. I've got a piece of aluminum turned to the 28mm ID of the swing arm and probably tomorrow I'll bore that for a good fit on some .75" shafting and put them into the swing arm and see how well things line up. Doing a test with some scrap aluminum is better than screwing up some bearing stock. Other than that I didn't do much with the KT today, spending the time instead doing some welding on the upper wheel yoke of my English wheel. It was nice to not have that screw up either. cheers, Michael

When did this "in section advisor" become common practice? I presume it was after the elimination of the no-stop rule as a minder wouldn't be of much use as anything but a " safety catcher" if you couldn't do all the hopping and backing and forthing. cheers, Michael

When I pulled the rear dampers I noticed that the swing arm would barely move unless I gave it a very strong push. When I removed it I found several problems. The center tube in the frame is .060"/1.5mm narrower than the space between the rubber silentbloc bushings. When the pivot spindle is tightened up the frame is drawn together, pushing the center bushing of the silentblocs in until they take up that clearance on the center tube. This removes the offset of the center bush on the outside of the swing arm and means the face of the swing arm rubs on the frame and wears as pictured below. I made a couple of small press tools to try and remove the silentblocs but they wouldn't budge with the vise, and I don't have a press. I'll probably just use a hole saw to cut the rubber out and then a small grinding point to cut through the outer case of the silentblocs. After the hacksaw attack: http://www.eurospares.com/graphics/trials/KT250nobottom.jpg Detail of dented frame tube: http://www.eurospares.com/graphics/trials/...ottomdetail.jpg Smeared/worn metal at the swing arm pivot: http://www.eurospares.com/graphics/trials/...0silentbloc.jpg cheers, Michael

I covered all of those questions from you in various posts over the last week or so. Those answers are still good, and you should be able to search out my posts and find them pretty quickly. That would be a faster answer for you than me typing them over again. cheers, Michael

Changing forks doesn't change the steering head angle. cheers, Michael

You'd need some sort of arbor made with a taper to match that in the flywheel. Have the same diameter at the points of the shaft that will be running on the balancer rollers. Your friendly neighborhood model engineer could probably turn that up for you. Then look at a wheel balancing stand, the kind that has four discs mounted to bearings that the axle sets on. You can make your own like these: http://www.nomartirechanger.com/ProductHer...iumBalancer.gif http://www.roadstarclinic.com/TechTips/Whe...ages/standf.JPG If you aren't noticing a lot more vibration than would seem appropriate you probably don't have a problem. cheers, Michael

It is the picture identified in the book as Alan Morewood with his Bultaco. It seemed unlikely that the English trials scene would be overflowing with people of that name, but then there are a few Michael Moore's in the world so I thought I'd ask him since he mentioned it just in case he had a cousin with the same name or something like that. Page 41 opposite the photo of the Miller Highboy frame. cheers, Michael

The steel bash plate (bashed) and the two frame rails (also bashed) it is welded to between the lower engine mounts weigh 2.5 lbf. The frame sprang apart pretty noticeably after doing the cuts. A square foot of 3/16" aluminum plate is about 2.6 lbf so there may prove to be no net savings by converting to a frame that is open under the engine. cheers, Michael

Is that your father pictured in Morely's Spanish trials bike book with his Bultaco? Is that you or your brother there with him? cheers, Michael

Here are some photos of different BSA-engined trials bikes for you to consider: CCM: Walwin: B25 in modified OEM frame: cheers, Michael

Meney TY250 with forward pivot and disc brake on the transmission countershaft. Concentric sprocket/pivot doesn't eliminate anti/pro squat effects in the rear end from the chain pull, but it does change them from the conventional setups. John Hemingway's McLaren Suzuki at the 1971 SSDT: cheers, Michael

34.5 lbf for the KT250 frame, coil and ignition box, swingarm and spindle, short rear brake stay arm, footpegs and brake pedal. I'll be interested to hear the Bultaco numbers. It was $25 for ITSA. That truck had a crane on the back of it. It also delivered my mill and picked up my manual mill to move it to the house of a friend who bought that and my bench lathe: We did get the mill stuck in the garage door until we took it off the skates and pinched it through. cheers, Michael

David, I joined up over at ITSA so I could see that. Thanks. KT-milly thanks for the info. How much lighter did the bike end up from stock after you went with the Gollner frame? I think last night I saw 26lbf on the scale for the frame with footpegs/brake lever/coil/spark box (no swing arm) with the swing arm being about 6.5lbf. I don't have my notes here in front of me but those should be pretty close numbers. Did the big bore cramp the transfer area at the case to the point where you had to add metal to the case to allow you to open them up? And might you have a nice high res photo that you could post of your bike from the side that shows all of it? Dave, one of the projects I've had sitting around is a table that will attach to the cross slide of my lathe so that I can attach things to it to align bore them. Until that is done I might be able to make a holder that would let me put the swing arm in a tool holder. That's something I'll look at today after I get the hubs shipped off. I think I've got a couple of tool blocks that accept a a 30mm tool shank. Maybe it will be the incentive to finally finish the boring table? I don't know if you're a tool guy but here's a photo of my lathe when it was delivered: cheers, Michael

It is the same thing you do when balancing a wheel. Put it on an arbor/axle on a stand with rollers for the axle to ride on and see if there is an obvious heavy spot. You've probably seen different flywheels (both mag and crankshaft) on bikes that have little drilled dimples on them where a small amount of metal has been removed to bring them into balance. If you've got a wheel balancing stand handy you are probably set once you make an arbor to hold the flywheel. Instead of going straight for the drill try sticking small lumps of clay on the side opposite the heavy spot until you get it to remain stationary in any position. You can get an idea from the clay of how much weight needs to be removed from the heavy spot. And of course, take a little less than you think is needed to start, and keep checking as you go along. The factories that make the flywheels probably have a dynamic balancing machine that spins the flywheels up and detects the out of balance spots, but that would be mainly to speed up the process. A static balance should be fine and you can do it at home. I'd presume that any factory part is probably OK and I wouldn't routinely check an OEM flywheel, especially if it looks like it has already been balanced. But I've taken apart some Japanese forks that came from the factory with the wrong bottoming cone on the damper rod that blocked off the bottom orifice on the rod, and I remember a /5 or /6 BMW that came into the dealership I worked at in the early 1970s that had the rear hub only partially machined, so even factories can screw up. That's why race tuners check everything in an engine, make sure all the rods are balanced and weigh the same, combustion chambers all match, brake pistons are retracting properly so the pads don't drag, etc. If you've got an aftermarket weight that bolts on to the face of the flywheel that weight might be perfectly made and perfectly in balance. But if the holes on the flywheel that it bolts on with or registers to are a bit off then the assembly is going to be out of balance. Or what if one of the three bolts that hold it on came from a different fastener manufacturer and is 1 or 2 mm longer or shorter than the others or has a little longer or shorter threads? 1mm off the bolt might not be much, but if it is out near the rim of the flywheel and you spin it up to 6000 rpm it might cause enough imblance to be significant. Might not too. A lot of the checking is done just so you know. A problem is that if you do find something out that you think should be fixed you then get stuck having to decide if you are going to do anything about it. Ignorance can bring bliss. BTW, if we're going to be discussing things would you do me a small favor and call me Michael? I've not had people (except elderly relatives) call me "Mike" for most of my life and if someone calls out "Mike!" or addresses a "Mike" in a post it doesn't normally occur to me to look around to see if they are talking to me. Thanks. cheers, Michael