ring gap ok?????
ET: Engine (Twin) Pistons found when barrels removed from my Rapide
- Thread starter Bogage
- Start date
as well as about 4-5 thou clearance?
If they have bodged that what else has been done.?? Look up "bodge" if you don't know what I mean. You are going to need new liners and/or pistons. Go with CP at 7.8:1. You really do not need more. If you want a softer bike go with 7.3. What cams do you have? Check the height of the barrels!! Make sure they are the same. Looking at the pistons I would also check seats, guides etc. I am going through a similar process for the first time in 20 years. It is something you need to have a clear head about because a short cut now can be a disaster.
Thanks much, I do know what bodge means to be sure. I’m not undertaking the work, an experienced fellow is assisting. He had not seen two differing pistons though. He will be checking the valve guides, etc as you mentioned. He’s very methodical, the reason he has it! I do appreciate the reply and input. The cylinders were standard bore so I’ve been informed that the pistons will be 20 over.
So right
Trevor. One of my liners fell out with a light tap and the other show carbon deposits 2/3 up from the base. It is probably a good idea to separate inner and muff for checking before fitting new pistons.
I very rarely reuse original liners, muffs, and pistons, as there are at least 6 items that can give trouble and it generally takes just one to cause more grief than it's worth. Here's a good example........I just stripped down a very original and unmolested series "D" engine from an enclosed model. It was running ok, though a bit tired and filling up the primary chain case with oil, due to too much blow by from the rings. After disassembly I found the bores were standard size with early Omega pistons. However the top of the liners had not been sealing in the head recess and the heads had been pulled down to at least 60 Ft Lb's......Thus the heads were sealing via the large broad alloy area. I checked the height of each alloy muff, one was 40 thou under and the other was about 50 thou. There were more issues as well, but I quickly decided to replace the lot, as this fixes many items in one go. Unfortunately I feel the upper and lower guides in the heads are out of alignment due to the excessive amount of torque applied to the hold down studs in an effort to make the heads seal, and this often cracks the heads as each Tower in the head starts to collapse. I learnt the hard way to measure up all the dimensions of old liners/muffs to see if they are still usable, but not many pass the test. It is a risk I am not prepared to take.
years ago I got the same problem till I noted that there was NOT enough clearance at the stud holes in the muff, so not enough expansion,
drilled them bigger and problem solved.
van Drenth JC
drilled them bigger and problem solved.
van Drenth JC