feetupfun

The front hub on the wheel with the gold rim is from an MH349. That hub is made by Honda and is notorious for spoke flanges breaking apart. The front wheel from the bike that was in the fire is the correct front rim and hub. Those hubs are very reliable and can provide good braking IF THEY ARE SET UP PROPERLY.

Mine is 205cc, WES end muffler, Yamaha main pipe, Boyesen reeds and John Cane ignition, standard carby attachment and standard size TY175B carby. The only rejetting mine needed from when it was 175cc was to go one size different on the pilot jet and slightly richer on the slide cutaway. It already had a smaller main jet than standard from when it was a 175cc and that stayed the same. I can go look up the specs if you want. David

One of my TY175s has been a test horse for modifications since I got it in 1976. The latest change I have made is to lengthen the swingarm by 45mm. The frame on this bike has already been changed in a way that has produced a steeper steering head angle but retained the standard wheelbase. It also has TY250B forks and a 205cc motor. The wheelbase before the swingarm extension was 48.5 inches, which is quite short for a trials bike. I felt it might be nicer to ride with a longer wheelbase and with the weight bias further forwards, so I decided to lengthen the swingarm to achieve this. I had heard that others had extended TY175 swingarms by between 25mm and 50mm. There are many ways to lengthen a TY175 swingarm but I decided to make new, longer axle mounting plates from 6mm x 50mm mild steel strip and weld them to the stubs of the existing axle plates. This avoided having to make new shockie mounts. Its probably not obvious in the photos, but the centre line of the new axle slot is lined up with the centre line of the swingarm side arms, which is also the case with the original axle slots. The length of the new axle slots and the location of the cam stops relative to the slot ends is also the same as for the standard setup. I made a cardboard template of the new axle plates, sized to have the axle slot 45mm further back than standard, and marked the cut line on the existing plates. I made the new axle plates from the template, carefully making them exactly the same shape and size and slot position. I ground a vee on one side of the new axle plates, cut the first axle plate off and made a matching vee on it. I then tacked the first new plate in position. I then ground a vee weld prep on the other side of that joint and welded it. I then welded the other side of the plate. I used a flat surface and a dummy axle to make sure that the second plate was going to be positioned exactly right and welded it on. I then welded on the cam stops, made from the shank of an 8mm steel bolt. The brake plate link is now too short so I am planning to make a longer one. The brake rod may be long enough as is, as I have rotated the brake arm on the spline. The chain needed a few extra links. The rear frame loop needed to be bent up a bit to provide tyre clearance at the rear end of the guard. I've ridden it since the mod and there is more weight on the front end as expected and the stability when turning uphill is much better. I can tell that the front wheel needs a wider arc in tight turns but it is still taking a smaller arc that my non-TY175 1970s twinshock trials bikes. The longer swingarm has also increased the travel of the rear wheel slightly, which has softened the rear suspension action nicely.

Before you go pulling it apart, my son's new GG50 also has an intermittent clunking noise which I found to be caused by an intermittent drive chain misalignment on the bottom run of the chain. The intermittent misalignment is due to the chain tensioner slipper causing the lower chain run to move left and right. The clunking happens when the chain starts to ride up the sprocket teeth, then jump back down into the correct position again.

You can use air or liquid pressure through the cam shaft hole to push the rod to the right hand end. Make sure that when it flies out it doesn't hurt anything in its path

Tap one end of the key remnant inwards with a flat-ended punch of a diameter slightly smaller than the width of the key and the other end of the key remnant should pop upwards. Keys can be made from a piece of mild steel of circular cross-section (round bar) with diameter turned to match the curvature of the curved side of the key. Cut key from piece of round using hacksaw or parting-off tool then hacksaw and file to finish. Alternatively you can buy keys from In Motion. The key is there only to get the flywheel to sit in the correct location while you tighten the nut and takes no part in the driving forces so should only ever be made of metal that is softer than the crankshaft, in case the taper allows slippage. A hard key may damage the crankshaft and/or flywheel keyways.

Standard carbies from DT175 ('74 to '88 models) and TY250B,C,D,N,R,Z will physically fit. The jetting will probably need attention.

No they would not fit the standard TY80 well at all - I just did some test fitting The rear Gonelli is way too wide to look right and would need a big piece cut out for the muffler to fit past. It is also the wrong radius of curvature for the TY80 rear wheel diameter The front Gonelli would fit width-wise but is the wrong radius of curvature for the TY80 fromt wheel Tha standard Yamaha TY80 guards fit perfectly

I do like the way you think Dave David Lahey

Usually new chains are too long straight out of the box for a standard bike. 11 39 on a Sherpa T sounds pretty standard so I would say yes you will probably have to take some links out to get it to the right length. Sometimes depending on sprocket sizes on Sherpa Ts with standard axle cams you might even need to use a one-and-a-half link to get the length right because they don't give much adjustment.

434 flywheel will fit 493 but has a lighter steel band/ring than 493

The cylinder nuts are 7mm internal hex and yes you can buy new ones

I have just tried another way to make the TXT Boy clutch engage at lower RPM and it works well. Someone in an earlier thread noticed that the parts list for the motor in the trials GG50 lists two clutch springs while the racing GG50 motor lists four springs and they postulated that some GG50 Boys had been fitted with motors with four spring clutches. I have not heard yet of anyone else taking two springs out but it is terrible riding weather here and a long weekend for me so I carefully pulled my son's bike's clutch cover off and had a look. Yes it had four springs and taking two springs out looked simple enough and the design is such that the change in the loading pattern on the pressure plate does not cause any problems so out they came. Amazing, it hooks up nicely a bit above idle now, it does not creep or drag, the manual clutch still works fine and there are no problems putting it in and out of gear with the motor running. Our GG 50 Boy was part of the first shipment of 2011 models to Australia.

The Aussie Trials site is www.trials.com.au here is a link to the forum string about the paint scheme http://www.trials.com.au/content/index.php?option=com_wrapper&view=wrapper&Itemid=7viewtopic.php&p=20898#p20898

Have another look at the Aussie trials site. I have just posted the photos you are thinking of

Before you get the case welded, fix the return stop mechanism or it will do it again. The stop device is on the kickstart shaft and the usual failure mode is that it slips (rotates on the shaft). You can fix it by getting a new kickstart shaft. The weld repair can be made smooth on the outside and can be poilshed but may still remain visible due to the colour of the weld metal being slightly different to the parent metal.

Has anyone yet tried using the standard plates and running with only two springs?

Oh yeah thats right Ross and the Pursang backing plate would need to be sleeved down.

Sorry for saying the obvious but you did not say how you were kicking it. Unless you are very tall, lengthening the kickstart lever will make it hard to get you boot high enough. Doubling the length will mean the end will hit your leg (or worse) If you lower the compression ala 1997 and later Techno motors you will find it easier to kick over compression. The 1994, 1995 and 1996 Technos take a much bigger kick to get over compression than the later (tamer) 97,98,99 model Technos. The suggestion to retard the ignition a bit would also help if you are feeling any kickback. I've never heard of a longer lever that fits the Techno motor and the Beta Rev 3 motors have a very short aluminium lever. Any competent metal fabricator could extend the existing lever if you are certain that is the way for you.

Yes they are all nice and there are no dud models as far as reliability goes. Do remember that the production of Sherpa Ts spanned about 17 years so you can expect that the earliest models will weigh a few kg more and have less ground clearance than the last models. Many technology and design improvements were introduced throughout those years but overall it was gradual evolution not radical change at any stage. To list all the changes over the years would be quite a list. If you are really interested, buy a copy of the book "historia de la sherpa T" by Francois Stauffacher. It is written in Spanish and English, well illustrated and msny of the changes are mentioned. There are quite a few minor detail changes that are not mentioned but the book tries to link changes to model designations, and in many cases the changes were just implemented at the convienience of the manufacturer as they became available, rather than waiting for the next model designation to be made. If you want the most competitive bike, go for the late models. Fortunately not everyone wants the late models so you see people enjoying Sherpa Ts that were made throughout the 17 years. As Dave said if you are heavy and/or ride at very high altitude or only do free riding, the 325 and 340 motors will pull harder than the 250s and 238s. If you are lightweight or not fit and want to compete in trials then the smaller motors will be easier on your body for kickstarting and riding in tight sections.

There are lots of possible causes for a poor spark not just a poor HT coil earth. also consider: Poor stator coil earth Capacitor condition Stator to magnets clearance Stator plate rotated away from ideal position Points dirty/wrong gap Poor connections in wiring Poor earth from motor to frame Leakage to earth via kill switch or points wiring MK8 Pursang front wheel should fit in the front end of a M199A. May need work on axle length, axle spacer and brake stay arm.

Yes the steel sleeves (inner bushes) can wear. They can also rust. With enough time and money, it is possible to convert your 349 to rolling element swingarm bearings but why would you when it is so much easier to just replace whatever is worn?

Stand on the LH side of the bike and kick it with your right leg

Gary I could only find one very dark photo of the LH side of the top of the motor on FB. That photo looks like a Cota 348 motor (310cc and made from 1976 to 1978) David