feetupfun

Our 2007 OSET 16 24V has seen a bit of use now and has had a few electrical component issues along the way, but has been quite sturdy mechanically until the drive pin for the motor sprocket sheared recently. My 21kg son was riding in a manner I consider quite normal at the time, practicing crossing timber railway sleepers on a gentle uphill slope. I know it is quite a simple job to replace the drive pin, but am wondering if it is a common failure or not, to help me decide whether I should use a different type of drive pin or the same again. The drive pin that it came with from new is a 3mm diameter steel roll pin.

OK this is my M49 that has been modified by threading a hole in the cable stopper and using an adjuster on the cable outer. There is also a little hole in the brake arm for a split pin used as a security device to prevent the cable end coming off the arm (required to meet safety specs in our trials competitions)

Ha, I thought you might say that. I actually could get a photo of my M49 front brake real easy because that end of the bike is sticking out, but was taken aback when I went and looked at it - I had forgotten that I had done the mod DabDab talked about on my M49. I didn't want to confuse things with a photo of something non-original so didn't take a photo. Maybe it would be OK though because mr MCman56 might be interested in what a modded one looks like. Yes - in about 6 hours a photo will be up here.

And here is my TY250A motor showing the hole/plug that searay is talking about

I've gotta go and have a look at mine the suspense is killing me Ok here is what a LH case from a TY250D looks like.

Dave the cable on the mcman56 Sherpa T runs down the rear of the fork slider so it is nothing like your later model set-up that runs down the front of the slider. I'm think your M49 cable runs down the back of the slider. David

The TY80 big-wheel fuel tank is too long for a TY175 unless you shorten the seat or move it back. I haven't tried a small-wheel TY80 tank on a TY175. I just re-read your post and because you said "gas" tank I figure you may not know what a big-wheel TY80 is. The TY80s sold in the US are small-wheel models.

As crude as it seems 30 years later, the cable outer simply buts up against the lug on the brake plate. What looks strange in your photo is that the brake arm is on backwards. Next you will be asking how the devil the cable nipple fits through that little hole in the lug. It doesn't. Another standard feature was removable nipples that use a screw to clamp the nipple to the cable. Unless someone has a photo handy, I will put up a photo showing the setup on my M49 Sherpa, which has the same design as your Alpina photo.

Most likely blocked pilot jet

I thought you said you had a TY250A?

The ring it is an interference fit on the flywheel and is also glued. It is not made to be removed and replaced easily. Removing it in one piece - say - in a press may damage the flywheel. Heating it to make it loose will damage the magnets. You could remove it safely by cutting it with a hacksaw, but then getting it to fit properly afterwards would require welding and machining. I suggest you try the lighter A model flywheel first on the C motor. It doesn't take much of a change in the weight of the ring to make a big difference to the motor response.

As well as the different porting between the A and later (B,C,D) models, the A also has a lighter flywheel. If you lighten the flywheel from what is standard on a later model (B,C,D) motor, it ends up similar to the A model in response. You can try the A model flywheel on your C motor before making any permanent changes to the C model flywheel to try it out. I have done quite a bit of experimenting on B and D model model motors and for me the ideal is to reduce the width of the steel band on the flywheel by about 8mm. Some riders like it even quicker response than that and run with the steel band removed completely. We very rarely ride mud here.

If you keep riding it, you risk that the bore, piston and rings will be damaged by the metal particles coming out of the bearing.

The flat slide thing in Twinshock trials has not been much of an issue here yet, but the upcoming 2010 Aussie Titles supp regs makes specific mention of carbys for Twinshock/Classic having to be "pre-86 design" whatever that means. If that requirement was to become part of the MA rule book, it might stuff things up for people who are using something so obviously non-period as an OKO or Keihin flat-slide carby.

199A frame has different ground clearance because of the alloy bashplate instead of the frame tubes. As far as I know the steering geometry and wheelbase are the same for both. sherpa325 if you are sure it is different geometry and have a 199A to measure please help out by providing the details required by Trials09. I had an idea why the wheelbase may be so short. I've seen people fit early Sherpa T swingarms to late model frames to shorten the wheelbase. It requires interesting mods to get the rear engine mounting arrangement to work but it is possible. Again photos will reveal all to people who know what Bultacos should look like.

M198 standard frame, standard forks topped out, standard triple clamps, shockie mount centres 345mm, rear axle in middle of slot, Michelin tyres with riding pressure - fork tube angle 28 degrees from vertical

I just noticed the amazing bit of plumbing where the exhaust pipe leaves the barrel. I've never seen a header pipe squeezed into such a tiny gap

OK I'll do a fork angle measurement. Topped out is what the suspension does when you support the bike under the motor with the wheels off the ground. It is called topped out because it is the other end of the stroke to being bottomed out. Are you saying your bike wheelbase is currently 3" longer than standard or 3"shorter than standard? Your story sounds very familiar. I think we have spoken on the phone a couple of times about this Bultaco and your 349. I also posted a few photos of what the Bultaco frame should look like at the front end on this forum or the Aussie forum David

Wheelbase 52.5 inches with both ends suspension topped out and rear axle halfway along slot. Sorry not able to measure steering head angle. Could measure fork tube angle if you are stuck.

Are you trying to use that mounting plate shown in the "before"photos? or did you also get a mounting plate from In Motion? The plate in your photos looks wrong to me. If you can wait a few days I will take a photo of what a 348 coil mount should look like. That chain tensioner may or may not be from a late 349, but the reason the chain has been rubbing is that it is adjusted way too loose. On my 348, I use a chain tensioner mounted to the motor in a similar way to that on yours, but mine has a shorter arm and works perfectly - bought from Jared Bates in the US. Your tank may be fine sticking out like that. I don't know for sure because our tanks (Australia) are a one-piece fibreglass item. What you have there with an aluminium tank under a fibreglass cover is what was sold in the UK. However it looks like the correct shape cover to me for a 348. Don't give up on your kickstart shaft and lever. There should be plenty of 348s around that are not worth fixing up and it is rare to see problems with the kickstart shaft spline and lever so you should be able to get one from someone wrecking one - even if you have to buy the whole motor to get it. Some caps have a breather built in and maybe your tank should have one of those caps. Can you do a better photo of the cap? The one-piece fibreglass tank 348s like mine have an obvious breather tube coming through the fibreglass ahead of the cap, and the cap is non-vented.

You can measure the fuel flow rate available to see if that is the problem. Dont clean anything or fiddle with anything until you have done the test or you might never know what the problem was. Take the (TK) carby off the bike so you can have it held over an icecream tub at the normal height and attitide it would be on the bike still with the fuel hose connected. Remove the float bowl drain plug Hold the carby over the tub and turn the fuel tap to on. See if the fuel flow rate out the bowl drain is weak (restriction in fuel flow), or starts off good but decays over time (insufficient venting of tank). Another thing that semetimes catches people out is if there is an uphill section in the fuel line, it can hold the fuel back if an air bubble forms at the highest part of the line.

TY250 forks are actually shorter than TY175, but when run flush with the top clamps provide the same front height as TY175 forks set to the standard 20mm above the top clamps. TY250 fork tubes are stiffer in bending, hence they flex less (so the steering feels better in dry rocky riding) TY250 forks when standard have a higher spring rate than standard TY175 forks and alternate springs are available (so they suit heavier riders). Having used both types of forks on my TY175 and weighing 94kg, I would say it is a worthwhile mod for heavier riders on TY175s. ausy300pro is spot-on about the appearance. While later model forks would probably have a better damping action, the TY250 forks do look era-correct on a TY175 or Majesty.

The last bike I saw that had the primary drive gears damaged like yours was a TY175. The kickstart knuckle clamping screw head had punched a piece out of the clutch casing and the piece had fallen inside. Instead of taking the cover off, the owner patched the hole from the outside. Eventually the piece of casing went between the gear mesh of the primary drive, bending the gearbox shaft and knocking pieces off the gear teeth on both gears in the process. My guess with yours is that something solid went through the gear mesh zone and bent the crankshaft in the process. By the number of damaged gear teeth on the driven gear, the rider kept riding it despite what must have been quite a crunchy-sounding motor. Yamahas motors are truly tough.

Maybe the problem with the Venhill cable length has been fixed since Woody bought his cable because I recently bought a Venhill TY250 twinshock clutch cable (through John Cane) and it worked without having to use a spacer (on my standard lever, original clutch plates TY250A).

Standard problem on those hubs. Yes most get sleeved in steel or cast iron. If you are doing it yourself the thing to watch out for is that there is not much thickness available in the hub.