XL Tillotson carburetor adjustment

[nh1520]

I posted earlier on acquiring a Homelite XL UT-104442 S/N: 780681245 and commenting on my initial clean up and related new parts (duckbill valves, new fuel lines, new Champion DJ7J plug etc).  The saw ran pretty good at WOT but would search for idle erratically from really high (chain moving) to low idle then die out.  I played with the L setting from seated out to approximately 4 turns and really no improvement.  Adjusting the idle would let me get it idling high, with the chain moving, but adjusting it down it would die out and stall.  It starts like a dream and will cut well as long as I'm putting the trigger to it - sit it down and eventually stall.  At this point - I'm fearing bad crank seals - but thought that maybe - just maybe - a carb kit would do the trick.



So I find that this saw has a Tillotson 4 carburetor on it and I immediately got a feeling of impending doom. I removed the carb and found the numbers HK2B627. I ordered an RK-32HK RK33HK kit that appeared to have the parts I needed.



While waiting for my kit - I made a video of dis-assembling the carburetor paying particular attention to the gasket placement.  I removed all the gaskets and screen and then soaked the carb in lemon juice for 2 days, then sprayed with carb cleaner, blew it dry and waited for the kit.  After soaking and the carb cleaner - the carb body was very clean and all passages that I could see were open.  I also marked and removed both the L and Idle screws to make sure they were clean, sprayed carb cleaner and re-installed. The kit arrived (new intake gasket too) so I carefully re-assembled in reverse order.  I installed the carb and prepared for my test fire.  To my dismay, it is now leaking a dark oily residue - so I'm thinking way too rich, but no adjustments that I can make seem to make any difference.  At this point - I'm stumped.  I have read that these carbs are very difficult to adjust - but wonder what I could be missing?

I also wonder why this saw has a Tillotson carb on it when everything I have read or seen in the manuals calls for a Walbro carb?  Is it possible to replace this carb with a Walbro carb that seems to be much more available than the Tillotson?  I appreciate any advice.

On a side note - I did find that an Oregon 27859 bar/chain combo fits this little saw perfectly.  It's a 140DGEA061 bar and S53 chain in the 3/8" low profile .050" gauge.  I hope that I can get this saw running correctly so I can run this new bar and chain.






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[nh1520]

Here is the Oregon 27859 that fits this saw.

[onlyhomelites]

The Tillotson HK was used for a couple of years in the mid-70's on the XL models. You'll find it referenced in the Revision 1 parts list: www.leonschainsawpartsandrepair.com/uploads/3/9/7/9/39792537/homelite_xl_automatic_chainsaw_ipl_24923_revision_1_2.pdf

You may have two issues here, but I'll tackle the "oily residue" first. Did you adjust or set the height of the fuel inlet lever arm? If not, it may be sticking open and allowing way too much fuel into the carburetor. The arm should be bent so that it is just level with the deck of the carburetor.

The rest of what you are describing is a classic sign of bad crank seals. If you were able to get the saw to idle a bit, my guess is turning it on it's side would kill it immediately. The good news is that really isn't a super tough job or really that expensive. A couple of crank seals, some RTV Blue and a hour or so on the bench will do it. Here's a short video I recently did that talks about this very job:

[nh1520]

Thank you for the advice. I have seen a few of your youtube videos and they are excellent, thank you for sharing your knowledge with those of us less fortunate lol. The link to the manual and exploded view of this Tillotson HK carb tells me that I assembled the carb correctly with respect to the gasket orientation. I almost had a nervous breakdown when replacing the needle, spring, and lever. The pin and needle/spring assembly on this carb is not held in by a screw - but instead slides into a slot to lock in place. I ended up reusing the old inlet lever arm but I did replace the needle. The new lever arm did not appear to be of as good of quality. The new needle, original spring and inlet lever worked freely after re-assembly - but I admit I did not check to see how level it was with the deck of the carb other than to depress the end of the lever down with the end of a ruler against the body (which looked OK).

Since I've gone this far and now have a good manual - I may attempt the crank seal replacements. I'll look for the 69407 seals but may have an experienced buddy of mine tackle the actual replacement and re-sealing. I will absolutely post back with any additional questions and how I made out.

[nh1520]

Well, I found out a few things this afternoon. First, the crank seals for this XL started with part number 94368 then to 07205 and finally 09108. Second, they are NLA. I did end up finding 2 seals NOS and should have them in a couple days. When I finally got the clutch and flywheel off [little pieces everywhere now - thank goodness I took pictures during the teardown] I ended up carefully prying and digging the old seals out which were probably original. My question now is that the crank has some "slight" up and down play now that the seals have been removed. Is this normal or should there be no up and down play with just the needle bearings and thrust washers?

[onlyhomelites]

Glad the video was of some use! These do have some up/down play even with brand new bearings. Not a ton, but some. The factory installed the seals with the crankcase split...I'm not sure you can install new ones by driving them in (never tried). I do know you need a light coat of RTV on the outer seal casing for optimal performance.

[nh1520]

There was quite a difference in the amount of up/down play before I removed the seals compared to after. I've been successful driving in new crank seals on my Husqvarna 288 XP - but this is an entirely different little animal for sure. Thanks again for the help - I'll be sure to post back.

[nh1520]

I have not gotten my little XL back together yet - but in the meantime, I wanted to post that it appears that Homelite bearing part number 12530 crosses to a Koyo BH-87. These are readily available on Amazon.

[onlyhomelites]

Great information, thank you for sharing that!

[nh1520]

The little XL is up and running. New crank seals, ring, needle bearings and re-sealed crankcase and added a new recoil rope. The XL fired right up - but even after soaking, cleaning and adding a gasket kit to the Tillotson carburetor - I still couldn't get it to idle. No amount of adjustment on the idle screw made any difference. In a final act of desperation - I took to a friend of mine who worked on Homelite chainsaws years ago and he also could not get the saw to idle. He ended up replacing the Tillotson carb with a Zama carb off a Homelite chainsaw that he checked over and this one has the low, high and idle adjustments and it runs great. I have not had the time to get the serial and model number off this "new" Zama carburetor, but I will post it when I do.

[onlyhomelites]

I'm glad to hear that you have the saw running good! Some carburetors really resist coming back to life, so it's good that he had another on hand.

[undee70ss]

Jan 24, 2018 7:52:21 GMT -5 nh1520 said:

I also wonder why this saw has a Tillotson carb on it when everything I have read or seen in the manuals calls for a Walbro carb?  Is it possible to replace this carb with a Walbro carb that seems to be much more available than the Tillotson?  I appreciate any advice.

Homelite used carbs from all 3 major manufacturers (Tillotson, Walbro, Zama) on the little XL's. When you replaced the carb, did you also replace the reed block? If so that could have also been the issue. 

[nh1520]

I will ask him if he replaced the reed block when installing the Zama carburetor. I'll take a bet and say that if the old reed block matched up - he didn't. Since I am so unfamiliar with this set-up - what are the symptoms of a defective reed block and how does one tell if they are defective? Great advice and support on this board - thanks to all.

[nh1520]

One additional question - over the years some of the 10-24 threaded holes on this XL have just about worn out. The 4 10-24 threaded holes in the crankcase halves are all worn to the point that there are only a few threads holding. The metal housing screw holes where the recoil cover attaches isn't much better. Other than small heli-coils (which I have never had any luck with) is it feasible to drill and re-tap to the next larger size. It appears that there would be enough metal in both areas to accomplish this? Would a thread cutting type bolt correct this problem as well?

[sweepleader]

The reeds usually can be visually inspected to determine if they are bad. Any cracks or breaks are bad. The reed should lay flat and snug against its seat, there must be no debris under it holding it off the seat. The seat must be clean and flat with no chips or breaks or cracks. This would apply to any reed anywhere. They are made of spring steel and can crack and deform, they are not salvageable by "bending" back to flat except in extreme NLA situations. I would buy a parts saw before attempting to salvage a bent reed to make a saw run.

If the holes are bad the only real solution is heli-coils or the like. Many saws are destroyed by drilling large holes for larger bolts. Thread cutting bolts are for Chinese assembly lines, not for repairs. They will very likely make a bad situation worse.

Heli-coils are not difficult, only demanding. You must use the correct drills and installation tools and you must use them correctly. Buy a kit with all the stuff, drill with the drill supplied. Follow the directions carefully. It is not hard to do and you will wonder why you ever had trouble with them. I messed up at first, count on redoing several before you get the technique. The kit will have more inserts than you need, when you screw up, use a small hammer on a sharp pick to bend the thread out into the center of the hole. Grab it with a diagonal cutter and just pull it out. Clear the treads with the heli-coil tap and insert a new insert. No big deal, takes 60 seconds. You will be glad you learned how because heli-coils are life savers.

[nh1520]

I have the #16 (11/64") drill bit, the 12-24 tap and the 12-24 1/2" and 3/4" bolts on hand - but the advice on the helicoil sounds right. I'll try it again when I get some time to tinker with it. I'll follow-up on the reed valve replacement too!

[undee70ss]

I asked because your pic of the Tillotson carb had the reed block attached ( black piece).

[sweepleader]

I don't know about this case but many saw bolts are 5/8" or 7/8" long, or any other measurable size as installed at the factory. Be sure the screws you use are the correct length, which would be long enough to use all the threads available in the hole, but NO longer. That will be the strongest possibility without busting out the bottom of the casting. Screws can exert tremendous axial force, that is why they hold things together and why they break castings when improperly chosen. Also be sure to clear out any liquid from the hole, it also can break the casting with hydraulic pressure as the screw is run down.

This lecture is over and is just for informational purposes, anyone who already knows this stuff will please disregard without being offended, eh?

[undee70ss]

Mar 3, 2018 15:48:15 GMT -5 sweepleader said:

I don't know about this case but many saw bolts are 5/8" or 7/8" long, or any other measurable size as installed at the factory. Be sure the screws you use are the correct length, which would be long enough to use all the threads available in the hole, but NO longer.

Some of the IPL,s give the length of the screws used. 

[onlyhomelites]

I agree with the other members on this one...avoid tapping to 12-24 unless as a last resort. Give the heli-coil a shot as you'll be removing slightly less metal. The casting around the starter holes is thin enough at 10-24...at 12-24 any overtightening can lead to a broken mount. Don't ask me how I know this!