Bent L screw on carb

[Inky]

Hi all,
First post, hope you can help...
I have I would say a basic to fair knowledge of the workings of a saw and have successfully resurrected my 034super -but without any experience at rebuilding etc; all i needed to do was clean it, reset the coil gap and tune it. It's a really good saw now -starts reliably first pull when warm and cuts well. So that's a bit of background, but i have a new problem...
I'm having trouble getting a consistent tune on my recently aquired 064. It starts and idles well for a bit and then goes all over the place and I can't seem to get it right. After looking at lots of threads on here i thought it sounded like the L was too rich and it was flooding once it was hot. Now I've discovered has a very slightly bent L screw. I'm assuming this will be the cause of at least some of the variation in idle I'm getting; does this sound right, or should i be looking deeper? What effect would you expect a bent screw to have? I'll get a carb kit regardless, and will at some point do a crankcase vac/ pressure test- I'm putting together a testing kit -just need to make a plate for the inlet and I'm right to go on that. Any advice appreciated. Many thanks in advance, Inky

 

[HarleyT]

No, a slightly bent screw is not likely to be your problem.

 

[HarleyT]

Take a visual look while you pull off the carb, look for a ripped intake boot, or bad fuel and impulse lines, especially if you have sloppy/worn/ripped av mounts. You should go through the carb correctly, but a bent mixture screw would be a special order part....

 

[Inky]

Ok thanks HarleyT looks like I have a learning experience ahead of me. Well i suppose that's why i got the saw...

 

[HarleyT]

Put up some pics.as you go, post them here, we love pics.

 

[Inky]

I pulled the carb and gave it a clean and it's idling much better now. (Carb kit coming as well). The carb boot looks ok from what i could see without further stripping, as does the impulse line. I'll leave it at that for now- unless she plays up over the next bit of work on the weekend. Thanks HarleyT for your input.

 

[tomdcoker]

I have owned 064 saw that the bearing on the PTO side was spinning in the case. Just a possible place for an air leak. Tom

 

[Inky]

I sure hope not, Tom. That would entail a bigger learning experience than i have time for at the moment. But thanks for the info, it all helps. Cheers, inky

 

[Little Al]

I pulled the carb and gave it a clean and it's idling much better now. (Carb kit coming as well). The carb boot looks ok from what i could see without further stripping, as does the impulse line. I'll leave it at that for now- unless she plays up over the next bit of work on the weekend. Thanks HarleyT for your input.

As said in post#2 a bent needle should not alter the setting . the setting may differ from what it would be with a straight needle but if a setting with reasonable running can be obtained it should stay at that setting. Have/did you check the the fuel delivery needle/arm for correct height setting? this if incorrect would affect idling/running

 

[Inky]

Yeah i did adjust the metering arm it was a little high so i made it level with the edges of that part of the carb- as i read somewhere on here. Looks to be an older carb- doesn't have the periscope type thingy on the top. If that makes sense..? Going off the ipl that is.

 

[Amp4027]

Inky, my new ms193T did the same thing. Couldn't get the damn thing to tune right and started to get extremely frustrated. Turns out: the needle screws were loose (and possibly the needle seats were not pressed in completely at ZAMA china), and were spinning themselves around as the saw vibrated at idle.
Fix? Take out the spark arrestor screen and scrub with stainless steel brush then spray with non-CL brake parts cleaner and reinstall. Take off & blast out the muffler with the non-CL brakeparts cleaner (at this time, you can look in there with a flashlight and see if you got any scoring going on). Buy a OEM weighted fuelfilter, and set the screws at default (whatever that is for your saw, 1L&1H or 1L&1.5H, and when finding 'lightly seated' use only your thumb and forefinger on your mini screwdriver, and seat and back off 3 times while lightly increasing your fingertorque to make sure it not just a hangup on the needlescrew threads, when you have them both 'lightly seated' visually verify both needlescrews are sticking out of the carb the same length) and then bring them out an extra 1/4th turn. Add blue loctite to the whole visible screwthreads then while still wet, turn them back in a 1/4turn, and then a hair more (like an 1/8th more, so you are now just a hair leaner than default carb settings - if you're uncomfortable with this then skip this step, but a 1L&1.5H saw with 1/4out on L & 3/4out on H factoryset limiter caps leaves your actual needlescrew adjustments at 0.75-1.5L&1-1.75H). Wait overnight. Run the saw for at least a tank of gas (not superhard, just wanting it to burn off any caked-on carbon and sludge) before making any adjustments while in the cut - I didn't have to besides just a hair on the H side to keep the limiter from kicking in during letting off the cut while WOT. After you find the perfect tune, let the saw idle for about 3 minutes, then cut again to be 100% sure, and shut the saw off at WOT. Then go loctite it again and don't touch it again unless you absolutely have to. Also, make sure you use a heavy EP grease (such as the blue synthetic brake caliper grease from O'rielly's) on the plastic to metal mating surfaces of the airbox to carb so you don't get any unfiltered air leaking into the engine, and torque the carbnuts to their correct specified spec.

Just saw that its an older non-strato carb, so its prolly 1L&1H, but check your service manual.

Whew, that was a bit of a novel... but I hope it helps.

 

[Inky]

Thanks Amp4027 that's helpful for sure. I do need to seal the airbox-it had some red gasket type material to seal it previously but it was peeling so i cleaned it off. I was wondering what to use to replace it so your suggestion was timely. And yeah I used 1 and 1 to start and it's tuned at about 1.25 and 1.25 which is about 2500 and 12000 revs. I'll give her a runand finetune today if i get a chance- we're carting hay so probably a full day... Thanks again., Inky

 

[Inky]

It turned out it was possibly a loose clamp on the carb boot, and definitely a crack in the fuel line. She's now running beautifully. Still not much to look at, though... (pic posted elsewhere, sorry for poor quality the lens on my phone is scratched)

 

[Inky]

... also the metering lever was way too high after the carb kit went in. Just thought i should mention that as it sort of rounds out the advice you all gave me- just about everything that people mentioned was wrong at some point. I sealed the airbox with red loctite gasket stuff so should be good to go. I would like to change over to the hd2 filter but that'll have to wait. Thanks All for your help. Inky

 

[bikemike]

Don't need the L needle if you keep it wfo till ur done with the job lol