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Update On Bultaco M159 Engine Assembly


sunny
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Thanks for all of the suggestions, help and personal messages offering assistance.

I have got the cases back together. I heated the right side in the kitchen oven when the wife was out and it slipped right on without even using a rubber hammer. I have now started to assemble the ignition/flywheel, the gearshift etc.... I just need to get a few new things a seal, a lock nut for the kickstart spring holding nut ( is that avaliable?), the four long studs to hold the cylinder and head, a new set of rings (which i have to figure out what size they are), a holding washer for the sprocket, so really not all that bad considering it came to me as a basket of parts that changed hands a few times before I got it.

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I was looking at the manuls and saw that there is a speciality tool for clutch spring installation and I thought that I could make something simular.... but as I worked my way through the boxes of bits I found this modified power driver bit from the previous owner so I decided to make an improved one using an old nutdriver.

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Sunny

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Well done Sunny,

looking good. A few points to watch out for to complete the build:

After fitting the clutch pushrod, remember to fit the ball bearing before the final clutch "mushroom" pushrod.

I'm not too sure about the clutch spring tool, looking at the extended LHS gear change shaft, you should have the later clutch spring posts with threaded adjustment - use a locking wire through these nuts if you do have this.

The locking nut on the kickstart spring stop was a pressed steel unit, you'd be fine with a standard M6 locking nut.

If you can't find any barrerl studs, I can measure up the ones on my spare 250 Sherpa motor for you to make up new ones.

Bye, PeterB.

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I may have those parts. I have a set of studs although I'm not positive that they are the correct length. I also have the lock washer for the sprocket. The seal will be available at any place that specializes in bearings. I know over here on the mainland I use Raeside but BC bearing or command bearing will likely have the seal and you will be surprised how inexpensive they are. Acme Bultaco will have the piston rings. On the top of the piston if it is oversize it will say ,25 or ,50 or whatever size it is. If there is no such mark then it is a standard size piston. Many times the piston will have other markings like T2+ or T2- these are designations that are used for final fitment of the piston in a freshly bored cylinder. Ignore this it has nothing to do with wether or not the piston is oversize and isn't critical now that the piston has been used before and is now being put back into service. My 159 uses the pin type clutch too and I actually made a tool for it to make them easy to install. You can do without it with some fiddling and a helper.

Looks Good

Steve

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Is there a brearing that goes in the clutch between the mushroom rod and the adjustable clutch plate? If so what size is it? It looks like the parts diagram shows this but difficult to make out.

thanks

Sunny

Yes, a radial bearing, at least on the ones I've looked at.

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Yes, a radial bearing, at least on the ones I've looked at.

Dave do you know the size and can I get this at a bearing supply? I got all of the oil seals at Western Equipment in Victoria they were very helpful but I had the sizes from the parts book.

Mike

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You'd be better off just contacting a Bultaco dealer/specialist such as Hugh's Bultaco as they may have one in stock, or a used one. You could probably have one before someone has looked up the part, measured it and you've chased around bearing stockists to see if they can get you one. From what I remember, there are no part numbers on that bearing.

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  • 1 month later...
 
  • 2 weeks later...

I got the rings and the clutch thrust bearing in the mail from Speed and Sport and as expected they were a perfect fit. I have the engine back together and in the frame a few things have come to light I think it matters which way the mounting bolts go. I had them going head to the left and nut to right and I think it should be the reverse and I also had trouble fitting the exhaust and the hanger that goes to the top rear engine mount bolt. I think I will have to pull the mounting bolts and exhaust out and start over. I tried to start it up the way it was but the petcock leaks like crazy. Can it be rebuild? It take all of my 240+ lbs to turn the engine over which I think means it has good compression. Finally, the throttle does not have a stop and the cable pops off. The list of new parts and things to fix got a little longer. Does anyone have a seat pan for a M159.

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I got the rings and the clutch thrust bearing in the mail from Speed and Sport and as expected they were a perfect fit. I have the engine back together and in the frame a few things have come to light I think it matters which way the mounting bolts go. I had them going head to the left and nut to right and I think it should be the reverse and I also had trouble fitting the exhaust and the hanger that goes to the top rear engine mount bolt. I think I will have to pull the mounting bolts and exhaust out and start over. I tried to start it up the way it was but the petcock leaks like crazy. Can it be rebuild? It take all of my 240+ lbs to turn the engine over which I think means it has good compression. Finally, the throttle does not have a stop and the cable pops off. The list of new parts and things to fix got a little longer. Does anyone have a seat pan for a M159.

Matt is good people. Get a new petcock.

Edited by swooshdave
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Looking good Sunny. Are you planning to use the bike in competition or just for weekend fun? The VMC holds trials events with a twin shock class. they are really fun and a good way to hone the skills . There are a few guys that regularly ride these events that are pretty tidy riders so winning is pretty tough (at least it was for me) but its still good fun. either way this should be a fun bike. good luck with the rest of your build, Fergie.

Edited by fergie
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