Hi colleagues,
I have a question for you that has puzzled me for a while. There is a knocking sound in my engine at idle speed ~1000rpm that disappears on higher rpm.
Lets start from basics:
- I have adjusted valve clearances i.e 0.10/0.15mm sharp.
- I have balanced the carbs.
- I have changed oil (semi 10w40) and filter.
- Sparks look OK i.e. no oil or anything unusual.
- The engine seems to run otherwise smoothly with power.
- It has 37000km on meter which might be even true.
- Still there is the noice, also with clutch pressed and gear engaged i.e. can't be the transmission.
- I have also tried to listen the noise if that changes when I release clutch smootly at idle revs and at the same time give a bit more power but still no change on voice => this test revealed rod bearing problem in some cases but not now.
- If I try to listen and localize the sound it seems to come either from valve mechanics in front cylinder or from lower, front crankcase.
My personal analysis lead to crank main bearings OR
it might be also rod but I am puzzled about that due analysis above OR
it might be piston but sound localization tells the opposite OR
it might be worn camshaft
So, Leute, any ideas?
BTW, Cold engine does not give that noice for some seconds, say 10s. Then the sound is at the worst during warming period. Fully warmed engine has the sound but not as bad as during warming period.
Pekka
5A8-1849 TR1 Silver bj81, Finland

Hi Pekka,
I had a similar problem a while ago. After I removed the oil supply lines (the ones that supply the valves with oil) and cleaned them by blowind air through them with a compressor, the knocking was gone. I suppose, that not enough oil went through them. If that doesn´t help, check if the oil pump is pumping oil enough oil to the cylinder heads.
Good luck
Andreas