Stubborn Chainsaw Running Issue

[Muddy42]

Thanks. Any tips on refitting these induction tubes / boots to ensure everything is airtight? I now have everything spotlessly cleaned with cotton buds. Should I use any lubrication on the contact surfaces with the cylinder, carb or on the hex screws ? 

[adw]

Whenever I have any issues with the 135/140/435 ( all the same platform ) I have stripped them right down, so it easy with the cylinder removed, no need to put anything between the cylinder and induction block when fitting.

[Muddy42]

Right. Ive replaced the input boot and the airleak problem is still there. I dont have a pressure tester, but I guess the next thing to check would be crankcase pressure and see if the seals are leaking.

[Muddy42]

 

 

 

[pleasant]

Do you have a can of carb spray with one of those long plastic nozzle adaptors? If so, set it up like you have and start it up. Gently spray the carb cleaner using the nozzle in or around the recoil area- ensure you don't get to close to the carb/filter area as you don't want a false reading. If you have a crank leak on the recoil, side then by spraying the carb spray in that specific area the revs will increase, or it will possibly stall due to it being too rich with the spray, but normally it will rev up momentarily. If you are unsure if you have a leak around the intake boot etc, then use the same trick- but like I say but a barrier between the intake boot and the carb intake. It's quick and easy. If you want to do it really properly, then remove the starter with the engine running to expose the flywheel, then apply the spray- just be very careful removing the recoil on a running engine. Would suggest before starting you remove three of the four screws and just leave those in place that take most of the pressure when pulling the rope. The ones you have left in place, loosen them first then lightly screw them back in before starting. That way less pressure will need to be applied to remove them. There are several videos on youtube showing this proceedure if you want to check them first if you are unsure.

 

Here's one for example:

 

 

Edited December 23, 2022 by pleasant

[adw]

Can we just go back what is actually wrong with the running of this saw? Are we just talking about the idle speed? Just to clarify.

[pleasant]

That last video shows it seemingly running very rich

[Muddy42]

1 hour ago, adw said:

Can we just go back what is actually wrong with the running of this saw? Are we just talking about the idle speed? Just to clarify.

1. difficult to tune - i think ive got everything set and then something changes, the saw stops idling or bogs.

 

2. cuts out when cutting wood at high rev.

 

3. idles rough, it sort of chugs, see video.

 

1 hour ago, pleasant said:

That last video shows it seemingly running very rich

true, but if I had L or idle set much lower it dies.

 

so far I have replaced fuel filter, carb and input hose. Ive checked all hoses for leaks. The piston and rings look fine from both sides.

 

ive given it to a friend for a second opinion who services saws as a hobby and is very good with them. Lets see.

[pleasant]

Symptoms seem to suggest an air leak......the carb seems all over the place

[pleasant]

Watch this video, and see if his symptoms ring bells with yours: