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Sherpa T 350 Engine Woes


saw miller
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Depends on the conrod kit and piston being used, as they're nearly all aftermarket now, but sometimes there is one full width bearing, sometimes two smaller. There can also be spacers to go between the conrod and piston.

That bike is far too good to be a parts bike.

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Not giving up yet. Guess that is why it ran so poorly. The rod and bore still look good. Will see about getting a new wrist pin and bearings. Might have to get another piston kit.

Expensive mistake on my part.

Tripp

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My piston kit came wit two bearings and two spacers. Unfortunately when I put it together I left one in the box. Looking back,I remember thinking to myself that the bearing seemed really narrow.

Guess I should consider myself lucky that more damage did not occur.

Tripp

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  • 2 weeks later...

Started breaking down the sherpa today. The stator side inner bearing race is spinning on the crank shaft. The plot thickens.

The bottom end kit arrived from Hugh's . Time to heat the cases and see if they will separate.

Tripp

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when you say the inner bearing race is spinning on the crank shaft. do you mean the outer edge off the bearing is spinning in the race off the crank case? if so that means the bearing race is worn? this can happen when the bearing has been taken out lots off time without heating the case up enough to allow the case to expand.

Edited by bondy
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Built a case separator afternoon. I attached it to the cases and heated them on a gas grill. The separator worked like a charm.

The stator side of the crankshaft seems to have issues. I can easily slide the old and new bearing on and off the shaft without heating the bearing. In fact all three bearings stayed in the cases when I separated them. Great fit in the cases. Bad fit on the shafts.

Seems that I need to have the crank looked at. May ship it to Hugh's.

Tripp

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  • 1 month later...

Split the cases and rebuilt the bottom end. Had the crank done by Hugh's. New seals and bearings throughout. New rings etc. Runs great. Blip the throttle hard twice in neutral and she runs away. Swapped in the carb from the other sherpa and it does the same thing. What next? I am at a dead end.

Tripp

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Hi saw miller,this is my first post having just joined. I am at present assembling a hybrid M 92 -M99 326 motor. Be aware only these 2 motors used a centre gasket of a particular size,all Bultaco centre gaskets look the same at a quick look. Worth checking. I always face my cases on a thick steel plate with fine grinding paste & a dash of diesel for 10 minutes or so. Surprising sometimes how many low spots show up because the cases are warped. I think your problem is a warped case. I now also use Viton seals on the crankshaft side of the motor.They are very expensive but are ethanol proof & last a lot longer than standard seals. A further check, the seal carriers are prone to cracking,have a look at that. On 2 of my bikes I have turned up from solid new seal carriers. Keep at it & let us know of any progress . I am John down on the Island of Jersey with 1 Lobito, 2 Alpinas & 1Metralla, all road usable.

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Johnjsy,

Sounds like you have a fine collection of bulls. Thank you for the input.

I removed and re sealed the intake yesterday and found no problem there.

I wish I had lapped the cases as you described, warping could be the problem. This sherpa does not have the original cases, they are from an alpina. The center case gasket seemed to fit very well.

I might t try spraying some carb cleaner around the engine today. I have not tried that since the rebuild..

Where did you pick up the Viton seals?

Tripp from Appling Georgia with two Sherpas and a head ache.

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