problem? big end connecting rod failure? and other ????s

[Aladdin91]

I have had (including one engine with a replacement crankshaft and connecting rod) 5 replacement engines in my motored bike.
Every single one of them died from big-end connecting rod bearings failing.

The solution turned out to be simple.
Reason for the failures was due to incorrect jetting causing detonation that was pounding out the connecting rod big-end bearing.

Typically the engine started to sound like it had more than the usual rattles and the vibration increased, till it got to the point where the rattles were so bad and the vibration so noticeable that it would be stupidity to continue on riding as the result would be total engine failure.

In my case the solution was to swap out the standard jet in the 80cc engine and replace it with a genuine Dellorto No 84, but the engine ran smoothest and made the most torque with a No 83 and made the best power with a No 82.

Using a No 84 jet reduced the engine temperature quite a bit, though it runs too rich at wide open throttle at very low rpm, i.e. just off idle to 2,000 rpm.
After that it's fine, when the engine is hot.

Fabian

Hey can you explain more about jetting im in the process

 

[tinochids]

I've the same problem with big end conrod bearings. I tried using caged ones and they failed in about 90km. Uncaged ones get better lubrication but failed in around 120km and the bad thing about them is that when they fail, the send debris into the jug, scratching it, causing loss of compression and jug failure. Am getting too few KM on this bike before costly repairs. Am not sure what I can do now

 

[DAMIEN1307]

This thread has now been locked, it was started in 2010, last reply before now was 2017.

Please do NOT ignore old thread warning that was in RED LETTERS before you started to type in the box just below that RED LETTER thread status warning to NOT revive old threads like this @tinochids.

Am not sure what I can do now

What you can do now is to start a brand new thread of your own explaining your problem in order to get help in this decade, not the last decade and a half ago when this thread was first started 14 years ago...lol.