288XP Idles Fast

[ChrisAdam45]

I have an old but new to me 288XP and after finding manuals in the beg for manuals thread I decided I should tune it. To make a long story short, when I tweak the L screw to where it runs best, it idles fast enough to move the chain with a pretty consistent 4 stroke sound rather than the hit & miss idle sound. I backed the throttle stop screw way out until it's no longer touching the throttle arm and it's still idling fast. Does the carb have some other throttle stop that I need to adjust? Does this mean I have a vacuum leak? The saw runs great otherwise.

Thanks.

 

[HiOctane]

Check if you dont have a worn throttle shaft where it meets the body and also look at the throttle shuetter if not worn on each side.Would make your saw turn fatser at idle.Does the saw revs up at idle or just running fast only ?

 

[ChrisAdam45]

Does the saw revs up at idle or just running fast only ?

It doesn't change or rev up on its own, it just idles high. I'll go wiggle on the throttle shaft and see what it feels like.
Thanks.

 

[shelbythedog]

Maybe the idle speed is correct and the clutch springs are worn out?

 

[JustinM]

Maybe the idle speed is correct and the clutch springs are worn out?

Good suggestion with regards to the chain moving, but that wouldnt explain the sound differences.

Ideally this is a saw I would pull out a tachometer for because it sounds odd & would be nice to know what is causing the fluctuation in idle. In your original post you mention that you played with the L screw & the "throttle" screw (Im assuming you mean the High screw). I presume that you have gone back & re-adjusted idle, correct? Somtimes you can have a perfectly idling saw but when you adjust L and H you end up having to go back and re-adjust the idle screw. I only mention it because in your post you say you only decided to adjust the carb based on reading the manual, so perhaps you dont have a lot of experience adjusting/tuning carburetors - and the steps to do so is often very poor in those manuals.

Madsens has a very clear & thorough tuning tutorial here.

 

[nmurph]

It has an air leak, mosly likely on the PTO side. It is a very easy fix as the seal sits in the oiler housing.

 

[ChrisAdam45]

Thanks. I guess I may have been a little misleading with my lack of correct nomenclature. The "Throttle stop screw" I was talking about is not a mixture screw (L or H), it is completely outside of the carburetor and makes mechanical contact with the throttle lever/bellcrank to control how far the throttle can close when you let go of the trigger. I think you're calling it the idle screw. I adjusted the L screw until the saw idled the best and then backed off the screw in question (I guess throttle stop isn't the right name) which brought the idle down a little but now I've backed it out so far that it no longer even touches the throttle shaft/lever and the saw still idles high. I have another good running 288xp here and I know what it should sound like at idle. This one idles with a bit higher RPM and a more steady sound as if the throttle is slightly open. That's what I meant by 4 stroking instead of the normal hit & miss idle sound.

I'll go read the tuning tutorial, thanks.

NMUPRH this is good news, I was afraid I was going to have to split the case to change any seals...

 

[ChrisAdam45]

So I pulled the clutch off, seal came out (the one between the oiler and the clutch right?) and I found that I can wiggle the crank up and down.... UHOH! I guess I'll pull the oiler off and see what's actually moving... could it just be shot bearings?

 

[nmurph]

No, the seal is in the oiler housing. You have to remove 3-4 screws from the oiler cover and the seal will come out with the cover. The FW is seated in the crankcase.
I still think you have an air leak if you can't get it to idle down with the L screw set.

 

[ChrisAdam45]

Thanks. I pulled the oiler and it has the seal pressed into it just like you said. I can now see the bearing clearly and it looks like the inner race is tight on the crank, outer race is tight in the case and there's a ton of play between the inner race, balls and outer race. I'm thinking this is good because the bearing is obviously the cheapest part here. I also think there's no way the seal could have been sealing well with the crank moving up and down so I think you hit it on the head that the saw was idling high because air was leaking in on the PTO side. Thanks!

How big a deal is it to split the case and swap the bearings? If I take it to somebody who's setup for this how much should they charge if I bring them the crankcase/crakshaft with everything else removed and I have the new bearings ready to go in so they just have to open it up and swap the bearings?

 

[nmurph]

I've got no idea what a business would charge. If you want to strip the saw down to the bare CC, I will split the case and replace the bearing. Alternatively, you can get a splitter from Bailey's (~$60) and do it yourself (I bought those bearings this week for $11. It sounds way more difficult than it is in reality.
Let me know, I don't mind.

 

[farrell]

splitting the case to replace the bearings is not a bad job. the best thing i learned from AS was when you are ready split the case toss it in the oven at a couple hundred degrees for ten minutes or so. the case expands quicker and the bearings and cranck should pull out easily. may need a bearing puller, just depends. most saw shops charge around fifty dollars an hour so if you completely strip the saw down to the point of splitting the case it wont cost you as much at a dealer.

 

[ChrisAdam45]

I've got no idea what a business would charge. If you want to strip the saw down to the bare CC, I will split the case and replace the bearing. Alternatively, you can get a splitter from Bailey's (~$60) and do it yourself (I bought those bearings this week for $11. It sounds way more difficult than it is in reality.
Let me know, I don't mind.

Thanks I may take you up on that.

 

[watsonr]

Where in Idaho are you Chris?

Air leak for sure, I just did an MS460 and the symptom was the same. Didn't matter what the adjustment was, it idled high. The cylinder was loose, you should check that also.

 

[ChrisAdam45]

Hi Randy I'm in Coeur d' Alene.

I have the saw down to bare CC now... well I couldn't get the flywheel off... The good news is that the piston & cylinder look great, I'll probably throw a new ring on when I put it back together. The piston/rod/crank seemed nice and tight together, so looks like I just need the main bearings and I'll have a nice solid saw.

I'll order up the gasket set and stuff tomorrow morning and start calling around about getting the bearings changed. Chances are I may box it up and send it to NMURPH, thanks again!

 

[watsonr]

Homelite Jim is near you. I grew up in Lewiston.

Hope you get the saw fixed at a decent price! Taking it in stripped down will save him time and you money for sure.

 

[nmurph]

Hi Randy I'm in Coeur d' Alene.

I have the saw down to bare CC now... well I couldn't get the flywheel off... The good news is that the piston & cylinder look great, I'll probably throw a new ring on when I put it back together. The piston/rod/crank seemed nice and tight together, so looks like I just need the main bearings and I'll have a nice solid saw.

I'll order up the gasket set and stuff tomorrow morning and start calling around about getting the bearings changed. Chances are I may box it up and send it to NMURPH, thanks again!

If you are sending the saw to me, PM me bf you order your parts.

Neal

 

[ChrisAdam45]

Thanks again for the help everyone. I got the saw all back together and it seems to be a great runner!