Hello all, recently inherited a 68 Bonnie. Several years ago it was taken on a ride, lost power, no compression. Upon tAking out spark plugs, could see dime size hole in one piston. I believe it is due to gasket failure, but won't know until tear down. Will the cases need to be split? Any advice would be appreciated, father lost interest, I am making this my winter project.
Top end, or complete rebuild
- Thread starter tgrath
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A lot depends on what you intend to do with the bike.
If you intend to keep it and ride it for a few years and expect decent reliability and performance, I would tear it down completely and check everything.
You have no idea what the condition of the bearings and shells are; how worn the crank journals may be or what may be in the sludge trap.
Since it's a winter project you will have plenty of time to tear it apart and do what's needed.
If you intend to keep it and ride it for a few years and expect decent reliability and performance, I would tear it down completely and check everything.
You have no idea what the condition of the bearings and shells are; how worn the crank journals may be or what may be in the sludge trap.
Since it's a winter project you will have plenty of time to tear it apart and do what's needed.
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Rocky is spot on. Do it right with a complete tear down. You will save yourself a lot of future grief. I know from experience.
I have to agree with Rocky and Carl, a complete tear down would be best.
Can't help you with a machinist, but there are many good parts dealers in the US: Baxter Cycle; British Cycle Supply and British Only are only a few.
I've shopped for parts in Canada, the US, England and New Zealand - wherever I could find what I needed via the magic of the internet.
Parts are not a problem; you can source nearly anything. If you have bike swap meets in your area, these are another good source. I am not familiar with your area regarding good vintage bike mechanics. GrandPaul, on this forum, restores classics for a living and does superb work. You might consider pulling your engine and shipping it to him. He, The Seeker, Rocky, and others will give you good advice and guidance here on the forum.
Thanks Carl, will check out those sites, pretty much a hands on person, I plan on doing all the work myself, I will start inquiring around about a good machinist. Others on the Internet have said don't use just any machinist, but someone familiar with these old bikes, so that's what I'll do.
That advice is spot on. 
I have a GREAT machinist. He's been doing ALL my engine machine work for about 30 years now. He does everything from industrial/diesel right down to 2-stroke minis. He's a Harley collector that used to ride Britbikes in his youth. Very reliable, reasonable pricing, and experienced at Britbike stuff as he's done well over twenty sets of Triumph cranks, heads, cylinders, etc. for me.
Insured shipping of carefully packed, double-boxed engine parts is actually quite reasonable with FedEx ground if you book online.
Insured shipping of carefully packed, double-boxed engine parts is actually quite reasonable with FedEx ground if you book online.
