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Old 09-29-2010, 02:20 PM
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cdues cdues is offline
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Default Saving a '71 Bultaco Alpina.

Back in March or so, came across a Craig's List ad for this '71 Bultaco Model 85 Alpina 250. Went to look at it, got it started and did the deal. Had a few concerns about the running worthiness of the bike that were soon confirmed.

1. Spark was weak and intermittent.
2. Clutch engagement was tricky, efforts to adjust went from too tight so it wouldn't kick or too loose and it wouldn't disengage.
3. Difficult to restart when hot.
4. Pumping clutch oil out the clutch side fill plug.
5. Leaky case gasket.
6. Horrible brushed on latex paint on frame and tank.

So the work began.
This is how she looked when we got her. Looks pretty good in the picture, but up close the horrible was more apparent.



Simply trouble shooting brought about this diagnosis:
1. Clutch paw is on magneto cover on left side of engine, blots were stripped out causing to much play when clutch lever was pulled, hence not enough pressure on clutch plate to properly adjust it.
2. Ignition coil was crap and magneto woodruff key was sheared (out of time)
3. Oil pumping out of fill plug meant bad oil seals on the crank shaft.

Efforts to tap the case so the magneto cover bolts would hold did not go quite as planned so the search went on for new (to me) cases, acquired on eBay for not much. Time to split the cases. Since we were going to do that, might as well replace all the bearings, gaskets and seals. Engine rebuild kit acquired from Hugh's Bultaco for not much.

So it begins:


Getting her to this point took about 11 minutes.


Engine out and both side covers off. This is the right side, crank balancer and clutch pack, since she's right side shift, that's the sift mechanism in the back.


Torque speck on those nuts is 75 libs/ft, so motor went into the vice (a motor stand would have helped) and some "special tools" were crafted to hold the crank and clutch in place to get those nuts loose and off.


And off, flywheel on the other side was removed and now the cases are ready to be split (and replaced) to transfer the crank and transmission to the new to me cases sourced from eBay.


Ug. Burned up paper gasket and signs of high heat. Not a surprise as she was pumping out out through the failed crank oil seal. And loosing compression all the while.


Many trips from the oven to the garage floor with many different hammers and a few burned fingers, pounding out the old bearings and driving in the new ones. Made the house smell oily for a week.


Cases cleaned and new bearings installed. Transmission starting to go back together. Critical aspect of this part of the rebuilt was to pre tension the kick start shaft/spring.


In goes the shift drum.


Right side case joined with left side, crank spins easily on new bearing. New gasket with a bit of RVT sealant in the hope the make the engine oil tight. C clamps to help it cure. Torque speck on the case bolts is only 7 lbs/ft. Of course, there are 14 of them.


Starting to put the primary side and clutch back on. Took the opportunity to clean the insides as much as possible. This is a wet clutch so I knew i wanted to make it oil tight (if possible). This was also the naughty side as this was the side the crank oil seal failed on.


There is a special spring compressor tool available to make installing the pressure plate easy. I used steady force and two different sizes of needle nose pliers to get it done. Later models of the Alpina had nuts to compress the springs and not these little plates and pins.


Back together and piston reinstalled. Slightly larger piston and cylinder, making her about a 262cc. Ring gap checked and ready for the cylinder.


And here's the cylinder back on. Probably spent 3 hours removing the remains of the old paper intake gasket.


Head back on and gently and evenly torqued down. Inconsistent tightness will cause the piston to detonate. Don't want that...


Frame ready to receive engine, etc.


Back together and ready to see if it worked. Turned out it did. Clean carb, timing set, everything properly torqued, fluid added and she came to life after about 10 kicks.


Now time to do something about that terrible latex paint.


Probably have 15 hours in stripping, sanding, filling, sanding, filling, sanding and painting the tank. She's red now and while the paint job isn't concourse, it is fine for actually riding her. More importantly, the tank no longer leaks.

Still need to fine tune the timing and put a shut off switch. The question marks at this point were:
1. Would she idle?
2. Would she restart once warm?
3. Would she shift gears?
4. Would that cleaned and rebuilt 39 year old Amal carb actually work?
5. Is this 39 year old Spanish two stroke engine oil tight?

Pleasantly, the answer to all those questions are yes. Feels really good as I've held each and every individual part of this bike in my hand and put it all back together.

Hard to put into words the awesome feeling of verifying all that effort and work paid off and I now have a well sorted vintage two stroke tirals bike.
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