Yamaha 8B 677 Will not start- How to adjust and finetune? (Pics attached)

[mrskipper]

Hi all,


So.... same engine new topic....
I went thru and cleaned the
- breaker points
- carburetor
- fuel filter and pretty much everything i could find

When cleaning the breaker points i checked for the timing using the static method at WOT and it was around 25 BTDC, so that looked good, but even although that the engine wouldn't start.


I can see there are a few things that can be adjusted and suspect causes the engine not to start, see attached pics.
Do you guys have any idea on what to do?
- The timing mark on the side that moves with the thtrottle i'm confused about (thought it should be static?)
- For for the cam follower i guess that the first mark is where it has to match for START and the second one for WOT, is that correct?
- Carb height, this is some strange carb with the float just floating there not attached to anything, so i guess i just let it be there?

Any other hints are welcome!

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[mrskipper]

No replies, but will comment this in case somebody else encounters the same for the record.
I think i figured it out:
The adjustment plate on the right is probably the adjustment plate for the timing comparison.
I assume that Yamaha back in the days made it adjustable and that it has to be calibrated against TDC. I assume that it's been done in the factory and it's correct so i will not poke at it - but if anybody has any tips on how to check for TDC some easy way please tell so i can doublecheck.

The adjustment thing on the carb is probably something that has to be set to get it calibrated against START and WOT.


I have not found this info any way but that's just my guessing.

Regarding why it would not start i assume it's the carburetor giving issues, when cleaning it the gaskets looked good but i will now replace them all and rebuild the fuel pump just to be safe and see.

 

[99yam40]

TDC pull spark plug and insert a dial gauge to measure piston movement while turning flywheel by hand back and forth,
or a wooden dowl.
some service manuals have the procedure and tell which direction to turn and how to set pointer exactly

Good compression, good spark at the correct time, and proper fuel to air mixture is all that is needed to have the cylinder to fire up.
have you checked all of these the best you can?

 

[mrskipper]

Hi all,

Thanks! Will doublecheck all that,
While looking into this i paid attention to the head gasket and noticed that it wasn't looking that good, so i will proceed to replace that and try the rest all over again

Thanks all for now... to be continued