Yes rechroming is an option but these forks shown are heavily pitted,the amount of work to prep these areas will add greatly to what is and expensive undertaking to start with.
Other 35mm forks may well fit as many earlier Japanese bikes ran 35mm or you have the option of going for secondhand originals as you have been offered on here.
Good luck.
The manufacturer I mentioned will in heavy cases just apply more hard chrome so it can be grinded down again to the specific diameter you need. They have written it down in the website I put a link too (sadly just in German), see there when you use google translate to look at the page in English.
You can repair them too, they can re realigned and get a new hardchrome surface too.
There should be too some manufactories in Irlenad and of course there are some in the UK.
You can also sent them to Wissing Hartchrom in Germany they do a very good job,
they have done already several stanchions for me:
The Mikuni VM is good and works good, you can replace it against something different but be aware that it will be costly to find the right jetting, needle and needle valve.
The the flat slide carbs can give a slightly better Performance but these are more picky about the right adjusting and jettingh then old style round slide carbs.
These skinny fork tubes works well but are flexible and in a slightly harder crash they simply bent.
I had my first crash with them in 82 in to get new stanchions wasn't a problem. Now its much more complicated.
What you can do is swap to a TY 250 fork with holes or a TY 250 mono forks, both works fine, I stil thing the mono works even better because of its overrun and I done it to my TY.
The rear shocks can be replaced to better.
A really good thing is to extend the swing arm 30mm, you need a new brake arm then too. I have made a CAD drawing for that so the longer arm can be cutted by laser and have likewise holes like the originals.
Mounting the engine reed cage of the 250cc model is a good fix, too get rid of all internal stuff of the airbox to get better breathe.
If you come along a 175 MX clutch case from 74 and 75 that is too an improvement then you got rid of the oil pump and it's casing too.
Also that can be bought separate, use google search with your carb brand and model together with choke and parts.
Just a bit of research ... how did you manage to crack that piece I have a TY with Mikuni VM with a likewise rubber from 1979 and it is still in very good condition, never heard about issues with this part but the one incident out of the rule can confirm the average ..
Try to use a hotter plug, they work better with a beit hotter plugs in general, how is the color of the plug:
- black,
- dark brown,
- light brown in the middel and dark Brown around,
- whitish to light Brown,
I'am now using for all old bikes slightly hotter plugs with very good effect deoending starting running and durability of the plugs in general.
Are the reeds still straight and do they close well, is the reed cage well sealed too?
If you want to stay with the AMAL and have a worn out needle please replace the needle jet too because it will be likewise if not even more worn out.
Another improvement is to replace the slide against one with chromed surface thus the slide and the bore of the carb doesn't eat up against each other.
Hansjörg Pfahler has made a batch of chromed slides fir AMAL carburators for Bultaco and Montesa bikes. You might give him a call for one, his Website is:
www.bultaco.de
Beat improvement is a dump against something that is not AMAL or BING.
Here Dell'Orto PHBH or a Mikuni VM will improve everything and too gas consumption.
OKO's as Mikuni clones can be OK too.
I switched from AMAL to Dell'Orto and the bike runs much better / crisper.
I use RH Motorradlacke a small German company that produces paint especially for motorcycles and motorcycle engines, very good products, nothing to claim very good against heat and they have or will custom make the color you need for whatever bike / engine and model you are looking for.
If I would be you I would look up EBay Gumtree or used parts motorcycle dealer for another hub or even better a complete wheel. You might too try to get a pair of Yamaha TY wheels so you have too the brakes sorted at once.
You can too use bits from Alpinas for example, do some research and look your way through offers.
My personal 2 cent opinion in cases where you just want a runner.
On 21.02.2018 at 10:38 AM, nigel dabster said:
im not sure back pressure so far from cylinder actually does anything? And on bultos we always lengthened first pipe till the factory did it too?
The different design layouts where dicussed in German Trialsport Magazine (GTM) by Felix Krahnstöver, but you can read all about a following article in GTM # 107 page 50 ffp. from February 1985 in an article written by Dr. Klaus Simon who was at that time a trials rider and engine engineer at Sachs, in the article he discussed the different possibilities / set ups für rear exhausts from one chamber absorber- to one chamber refection and to the combination of both and where where where the advatages and disadvantages and very important how to construct them*. The article recieved special attention by the readers so he wrote two additional about trials exhausts for Twinshocks and Monos:
In GTM # 128 page 86 ffp. about the outtake or missing pipe and the mid section of trials machines and how to construct them*,
In GTM # 205 page 58 ffp. about the loading effects of two stroke pipes in trials machines and about their deimensions*.
* giving rules of thump and ranges to what ever you want to archive.
To two stroke engines with the technology of twinshocks and air cooled monos these principles are still valid today,
you apply them perfect to most new aftermarket exhausts, if you would take port steering or other more advanceed motor control unit
too in consideration there would be a design change of the given numbers in need.
To back pressure, it is a fact that a standard two stroke engine needs a bit of support depending air mixture flush from the exhaust side to work well, you can't change physics.
I don't think the Banana style exhaust is better then the clubfoot style and to me there are two reason.
The first is very obvious the clubfoot offers better sound reduction so is quiter.
The second is obvious too, the clubfoot offers more througput or flow rate as the diameter of the two tubes are bigger then the one at the banana type.
Second the Clubfoot offers more general back pressure in the exhaust system through the mace of voids, tubes and "windows" which allows a mild rearloadingeffect to the charge of air gasoline mixture which was pushed out of the cylinder.
The Banana style exhaust was an interims solution and invented after the tobacco pouch style rear muffler which did not show any good effect.
I thought so too but I'm a tiny bit concerned about the material as I always thought that carbon is a bit more sturdy then steel and when I mounted them they where perfectly straight an sat flush with the cage.
Additional I haven't had any differences in starting so far which would have been one reason for a reed malfunction.
I've ordered too another pair so in case of:
- I' am starting to get uncomfortable to whatever reason
- the reeds would now bend quickly to the other side and perform not as good as before.
Than I can easily switch, just now cutting a new seal for the cage cylinder mount ... also very important to avoid air leaks.
Hi, just doing the winter maintained to the bikes and did a look at the reeds of my TR 34.
What I found was that the upper reeds mounted to the cage are not aligned to opening of the cage anymore, instead they have "bent" which is about 1 deg.
Beside that only a tiny little bit of wear (fuzzy edge) is noticeable at the right reed towards the middle front. I never have experienced a different wear on carbon reeds never so far bent reeds*, should i keep or replace?
*To steel reeds that they start to bent I have seen but so far not to carbon.
Your thoughts?
You can see how they had opened inside and where the gas air mix has cleaned the walls and where there was turbulence in the air stream, very interesting.
Don't look bad but the upper reeds are now bend up instead of being alinged:
But I now have to correct myself if it is the very big thread which is in likewise diameter then the exhaust port then I would recommend laser welding which can be done without overstressing the old cylinder.
A good repair shop that will do this but in Germany:
They do all things you need to do too repair two strokes they tune scooters in all sizes vintage and modern. These guy have a cylinder of my bike just now and are reshaping the ports and in- and outtake + reshaping the head for better performance. Nice guys easy to talk and to negotiate with.
I like Würth Time Sert very much these are a bit more "durable" espacially for threads that have to carry a lot of stress.
I've repaired the threads to the rear shock mount to my Bultaco Sherpa and one mount to the bash plate mount to my
SWM with them, with very good result:
You find them at E-Bay the initial package is worth the money. Look up Time Sert and M 8 f.e.
I recommend that you use the side stand providet by Martin, the remake is in nice quality, the bend of the side stand is slightly softer but beside that very near by.
Here the measurements, the lower drawing shows a braket that would fit to an Aluminium swing arm:
If you take k/s off, frequently the threads on the allen bolt get damaged, check and replace if necessary. The replacement must be no longer than original or will damage the casing. Your casing saver should have a rubber pad on it, Martin M can help or glue a lump on.
Very important I had to replace the shaft due it leaked. To replace the shaft you have to take the complete engine apart, no other fix possible. Also You might look up a kick starter stop so you don't crack the casing in case you went a bit to far with the kick starter, (Martin has them).
Carb adjustmets that fitt very well from:
sea-level up to 1.500 above sea level:
main jet: 90
idle jet: 60
needle jet: AV 266,
needle: X2 2nd clip
choke jet: 65
gas valve: 200
float: 8gr.
slide type: 60
To the adjustment I can't tell you, I first apply a bit more idle through the idle screw.
Then I adjust the petrol screw, which I then turn out 2 rev.
Then by slowly turning in I try to reach peak of rev., if this does not happen I turn slowly out to find peak of rev.
If you turn in the screw completely the engune will die.
Where you have the peak of rev. there is the proper position which might vary a bit due to weather and height.
I never had to change jets between 50m up 1500m above sea level, first above 1500m you might try a 100 main jet which is again sufficient up to 3000m in my experience.
I can sent you measurements of the location and size of the sidestand amboss (mount) and the sidestand itself so you can let it be done by a local metal worker. The sidestand itself is also available from Martin Matthews.
To the mod's the foot pegs are a good modification but with welding around to the frame of the bike the bike will loose the road worthiness if you don't have a proof that it has been done by a specialist that is approved to do so, (at least where I live mandantory).
Other mod's easier to do are:
- replacing the fork from Marzocchi to later Betors by still using the Marzoccie Yokes / triple clamps of the one year later model.
- clutch fix from enduro model does help a little to lighten the clutch pull,
- side case from Aprilla TXR which helps a lot,
- HTX 740 oil which improves clutch engagement and stops the glue effect,
- aluminium swing arm which is lighter, a bit longer and stiffer,
In need I can give you the measurements of the side stand which I personal find is mounted very well to the steel swing arm.
To the gas tank the plastic gas tank is an improvement and much lighter also prune to dents and a bit more to wear in general too.
Martin is a good ressource in the UK.
I kept mine original but have technical improved rebuild most parts beside the paint, plastics, ... I like the patina very much.
During a tour in the mountains, note the side stand and how well it tuck it self away.
How the bike looks today with the modifictad fork:
The kickstarter shaft is much too long to be used without the support of ignition casing,
as it is now bent it is time to get the shaft out to get it straightened again,
there is sadly no other fix without overstressing the engine casings and bearings as I know.
I don't think it has to do anything with capacitaors, These are regulary just mounted to point's ignition to cut off voltage peaks generated by the points so they don't burn themself away while operating.
It's an electronic ignition, so there won't be any capacitaors, instead thrysistors wich are well cast inside the coil with also have electronics inside.
I would discuss this issue with Ewald, and to his English I don't know but think he can speak some English at least, try to keep sentence simple and short, I would too suggest to speak slow and pronounce well then it should be hopefully not too dificult.
Oh and he has an heavy Austrian dialect this will have an impact in his English speech too...
Pursang 370 stancions
in Bultaco
Posted
The manufacturer I mentioned will in heavy cases just apply more hard chrome so it can be grinded down again to the specific diameter you need. They have written it down in the website I put a link too (sadly just in German), see there when you use google translate to look at the page in English.