Hitchcocks Forum

Hi i have a 1963 250 Clipper the big end bolts have worked loose, i have the engine out. I want to no if i can split engine on right handside but leave left side untouched i.e camshaft etc. Regards Mik S.

Not being a true Enfield man I confess to not knowing the answer. Somebody will be along soon to answer your question.


However your question raises another fundamantal question or two. If the big end bolts have worked loose as you say, then how did that happen? Have you recently rebuilt the engine and if so did you re-use the original boltes? If you did then that is why they have come loose.


What damage has been done to the crank pin?


These are all far more important IMHO than trying to avoid a full strip down.


Are you intending to retighten the bolts? If you are then DON'T.


Big end bolts should be tightened with a torque wrench. They are designed to stretch by a fixed amount when torqued up during the tightening process to maximise their effectiveness in a very highly streesed situation.  They do not recover when loosened and any subsequent retorquing will undoubtedly cause a catastrophic failure of one or more bolts with subsequent and equally catastrophic damage to your engine.


Assuming you have plain metal big ends then strip them, check the journals for size and damage, regring or replace if necessary. Fit new shells and most definitely fit NEW BOLTS.


  

Thanks for your reply madmike,i got this bike off my brother in law he had it for ten years.It was supposedly rebuilt when he bought it,but it looks as if its been a bodge job. MikeS

Mike another thought occurs to me. Assuming you haven't stripped the engine, hence your query, how do you know the big end bolts are loose?

Hi i have taken head and barrel off to put new valve guides in to solve a smoking issue. I took barrel off to check big end for wear. Mike S

Hi again Mike. My apologies for being pedantic, but how did you deduce the big end bolts were loose by removing the barrel and head? Removing them will give you access to the piston and conrod, but not the big end bolts. So please don't be offended but can you explian how you decided the bolts were loose please. Thanks.

Hi i could lift the conrod up and down with barrel off, i now have it stripped down.I will have to put new big end shells new bolts and a new offside roller bearing in.i have split crankcase in halve leaving nearside complete.