What's on your bench today?

[Le Sanglier]

I would say that 30 months is a bit young for seals, in my experience, they go from a rubber state to a rock hard ceramic like hardness in time.

 

I have done pretty much successful vacuum tests and on moving the crank or pushing on it, got a leak and a bad one when these seals go hard.

 

A compression test will only let you know that your top end (piston, rings and bore) are sealing well. The pressure/vacuum test ensures the bottom end holds pressure and vacuum ensuring that air isnt being drawn in via anywhere but the carb on the upward stroke or leaking out on the downward stroke.

 

30 months old is a difficult one - it should have a decent carb at that age and the rubber parts should be OK - have you checked the gauze filter in the pumping section of the carb - that can give issues. Worth checking the tank vent as well!

 

Thanks all! I'll take it back for 1 more try to the shop.

[agg221]

Any thoughts on an unhappy 026?

 

For some reason my wife thought I shouldn't spend the day on the roof, so I did various bits and pieces, including cutting some firewood with the 026.

 

It started fine cold, and revved up well. Set it down and it idled now nicely, the chain just not moving. After a couple of seconds the idle revs dropped a bit lower, but it would still idle as long as I left it.

 

Pick it back up and it stumbled a bit, but didn't stall and holding it the revs would pick straight back up to the slow idle point. However, the slightest touch on the throttle and it stalled. It would then re-start immediately (first or second pull) and idle very low, but pull the throttle and it would open up and run fine.

 

If instead of leaving it running between cuts I turned it off, it would re-start fine, but stall when I touched the throttle. The only way to use it was to stall it between cuts, unless there was no more than a few seconds between them.

 

I'm anticipating that it's a flooding type problem, but any guesses where I'm looking? It's throwing me slightly that it will still idle well if flooding. I haven't dismantled anything in between uses, so it's not that I've put something together the wrong way, although something could of course have always been wrong since I bought it.

 

Alec

[Rich2484]

Sounds like air is greeting in. I've had it many times and it wa this.

 

Could be needle valve aswell. Either not opening enough or too much. Pressure test and vac test.

[agg221]

Sounds like air is greeting in. I've had it many times and it wa this.

 

Could be needle valve aswell. Either not opening enough or too much. Pressure test and vac test.

 

I've tended to think of air leaks as resulting in lean running, and hence the revs climbing rather than dropping, but pressure and vac testing would probably be a good idea anyway - looks like it will be turning up on this thread again as 'what's on Spud's bench today' I'll have a look at the needle valve though anyway.

 

Alec

[Rich2484]

Depends. If the crank seals are gone then it will die on throttle due to too much air getting into the crank when the throttle is pulled and the butterfly's open. Allowing too much air to fuel to go in in one go and stalling it out.

[agg221]

Depends. If the crank seals are gone then it will die on throttle due to too much air getting into the crank when the throttle is pulled and the butterfly's open. Allowing too much air to fuel to go in in one go and stalling it out.

 

I would have expected that to happen every time though, rather than being able to rev it up normally once re-started? It also doesn't sound fast. The revs are if anything on the low side (where I tend to leave them) and they haven't climbed. It will be tested to make sure though.

 

Alec

[Rich2484]

Ok. Start with giving the carb a good clean out then.

[agg221]

What do you stick in the ultrasonic bath for carbs?

 

Alec

[spudulike]

Just catching up, Alec - your 026 has symptoms of a slight air leak - I have had a few and they usually result in a variable idle speed that no amount of carb tuning gets rid of and also holding on to the revs when the throttle is shut off from high speed running.

 

It may be that the carb L screw is set a bit rich - if let idleing for a few minutes - when you grab the throttle, does it smoke a bit?

 

The 024/036 are a bit fussy on the L screw, too rich and they blow back a bit straight on to the air filter which then stifles the airflow. I tune them as lean on the L screw as I can to get the idle and pickup right!

 

It could be a worn L screw seat, had this before and it was a right PITA:thumbdown:

 

I use white spirit in my cleaner bu am careful about heat building up in the fluid - best stick to water and additive if the unit has a higher output:blushing:

[agg221]

Thanks Spud and Rich for your help.

 

It doesn't show the same symptoms as my 066 did when it had an air leak. It idles down quickly, to a stable, consistent point which hasn't changed as the chain is still just on the edge of moving. When revved out, the pick-up is good and the revs are stable and don't climb. My experience of air-leak failure is limited (fortunately!) to one, but this saw is not doing the same things as my previous experience, hence my further questions.

 

The only things it's doing differently from normal are that the revs drop that little bit more a couple of seconds later - again it's consistent, and it's not much as I can only just hear the engine note change. I can't test what happens if you rev up after idling - it does the idling bit, but not the revving up as it consistently dies.

 

I will take the carb off and give it a clean - I've run neat acetone in ultrasonic baths before which gets a bit exciting at times, but I won't go that route this time as my kitchen ceiling is quite low. I'll see if this helps, but it's worth pressure and vacuum testing it anyway I think. Is there anything hidden to look for when taking the carb off? I haven't worked on a saw this small before and it looks very fiddly compared to an 076!

 

Alec