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Misc Model191 Questions


herman
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As I move forward with my 191 resto, it is apparent that I'm going to need to change out the crank bearings. Does this engine use two or three bearings?

The engine has an 85 mm wiseco piston ready to slip in and I was wondering the best route on the small end bearing. Do I have to use the two spacers or can I opt for the wider bearing? Seems the wider bearing would allow movement.... Just don't know. 

Last: I hate the pin setup on the clutch hub. Any issues switching that out to the threaded type.?

thanks for any help.

Herman

 

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As I found with my M80 when rebuilding the crankshaft there are one or two differences that need to be watched for. In Motion sorted the parts for me but I ended up with a small end that needed spacers to my mind, but In Motion assured me that no spacers were needed. Bultaco relied on the minimal side play in the big end to keep the con rod aligned; however In Motion supplied me with a couple of spacers that did the job perfectly. Here are a few pictures to show differences in old and new bearings and con rod. The small end spacers used were stepped. Needles to say after sorting it all out I was very pleased with the finished result, even though you cannot see it. 

Crankshaft main bearings you can either go with one each side and gain in less frictional losses or fit two main bearings on the drive side for added strength. The crankshaft oil seals again you can fit one each side, but most including me have two seals on each side and these are fitted back to back to prevent crankcase compression loss and to help prevent air being drawn in. 

Hope this helps??

CA423CC7-BF1C-4C93-A953-BF9D7AEAE5C4.jpeg

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2B395CFF-F415-41E9-AF85-4944B11EFFD3.jpeg

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Hi, remember there are two separate end floats in the little end, and each needs to be independent of the other...

1.  The needle roller cage needs to be free within the little end, as the cage needs to move ( it rocks at half the speed of the rollers.)   In the above photo, it's 19.5mm within the 20mm eye, = 0.5mm slack.

2.  Then the little end eye and spacers need some slack on the piston gudgeon pin, maybe 1 or 2 mm, but this might be specified somewhere.

.

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Sci-fi, there were no little end spacers supplied, when I queried this I was told that Bultaco used the con rod thrust washers to keep the con rod aligned and therefore no spacers/ shims need in the little end. That means that the little end can flop about sideways an alarming amount in my mind, that is why I asked InMotion for some spacers which did the trick. 0.5 mm is not a lot of free play 0.25 mm per side. Bearing in mind that there is very little sideways movement in my big end/ con rod I can see Bultaco point of view. But I’m happier knowing the end float is contained to acceptable limits. Little/small end clearance at 1 mm might not be enough when heat expansion has occurred. My major concern was that if the little end could slide about sideways t high revs it might decide to chase into the piston gudgeon pin bosses. InMotion were very helpful and a mine of information and very quick with supplying parts.

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To answer your question about 2 or 3 crank bearings have a look at the Primary side crank seal holder. If it has a long inner sleeve on it then it only uses one bearing on that side. I think most of the Sherpas only use one bearing on each side. A lot of the Pursangs and other high performance engines use 2 bearings on the primary side. Graham.

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Yeah - I ran into a last minute need for a plate the night before our club's trial.... I have since removed the Suzuki plate and even sold the bike!

I'm getting good vibes about this 191, though. Disassembly went smooth - doesn't it always? And when the swingarm bolt came out without protest, I just had a good feeling about it. I haven't gotten as far as removing the clutch side, but did pop the flywheel and ignition to find that the bearing retainer appeared black. That's when I decided to get with Inmotion and get new bearings.

I have a shelf full of new stuff to put on and even plan on popping for new shocks. I'll have a fortune in her but what the hell? My only sore spot is the gas tank. It's pretty solid but has three unfinished fiberglass repairs. My first choice is to try and finish these spots as well as I can, give it a paint job and enjoy. Choice two is a plastic tank from a red model 199 that I have. I found that it would fit ok. Choice three is to keep watching for an old Campeon setup.

 

When I bought this bike I told my riding partner that I had a feeling that this one was going to be the most fun of all my bikes.

I'll post some pics as I progress.

Herman

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