Well I've been fixing up this 028 from like 1983 (I think) for my neighbor. Finally got the e-clip for the chain brake today. Went to fire it up and it would start, rev up, then immediately die the minute I took it off choke or tried to blip the throttle. I thought I had taken apart the carb to clean it but when I saw it I thought to myself "This does NOT look familiar". It's a Borg Warner carb.......and there's no diaphragm on one side. The metering diaphragm is there on the opposite end. Is this normal?? It did not appear to be dirty. I'll do a pressure test on the fuel line to see if that's it and replace the fuel filter too. It's definitely getting fuel because it otherwise wouldn't start but I'm guessing the missing diaphragm is the culprit, no? This is when I was like "WHERE'S THE BEEF???" Unless that thick rubber thing is the diaphragm? I just ordered a Walbro WT-16B carb on eBay. Hopefully that does the trick. This carb seems to fit properly - the entire carb is titled and the fuel and impulse connections are where they are supposed to be, as is the throttle connection point so I'm confused. All the carbs I've ever seen (which is not too many and thus why I am asking) have had thin plastic diaphragms.
Looks like a Frankencarb. I’ve never seen Borg Warner except on a torque converter. It’s wearing a tillotson pump cover. What’s the carb model stamped on the side.
Is it the HU 51C? Check to see if the diaphragm and the gasket have just married each other. Sometime they can look like one but can pulled apart. Either way, looks like there’s gasket thickness where there should be and thin check valves and chamber room where that’s meant to be. Repair kit at the bottom of the pic. If it is the hu, there should be a gasket and diaphragm
And this rebuild kit for the HU40B definitely shows a thin plastic diaphragm that is missing from mine. Wth!!! Stihl Chainsaw 028 Carburetor Tillotson HU40A HU40B HU40C HU40D Carb Kit DI 23584 If the saw came with the Tillotson but I throw a Walbro on there, will it still perform properly? I would imagine so but what do I know?
the above repair kit is what you’d want if you were going to go that route. I think the gasket is just tight to the diaphragm.
if it’s dying when you take it off choke or if your blipping the the throttle, I’d say your adding more air than carb can match fuel for. Either there is an air leak not controlled elsewhere adding un planned for air or there’s or a clog on the fuel supply; filter or carb. Fuel to air ratio is the basis.
You're right. I'm getting old man. Can't see any more. I think getting a new carb was probably the right call though. This thing looks OLD. Thanks.
I'll put a new fuel filter on it tomorrow but the gaskets are shot in the carb and that weird cover with Borg Warner on it has me befuddled. I'll try spraying some brake clean after it starts to see if I can find an air leak. Hopefully not.
id say the cover is oem for the time You could also open up the H and L jets to let more fuel in. That will tell you something. If your 2 turns out or more and it runs better, there’s an opportunity to make something else right.
This pic from HLS shows a different top cover than the one on mine...but it is possible that 40 years ago they used a different top piece. Stihl 028 OEM Tillotson carburetor I had tried that to no avail. Same behavior - would start, and the minute I'd take it off choke it would die. I don't think I went to 2 full turns but started at 1 turn out. Too late now since the gaskets are basically disintegrated from removing them. Will have to wait for the Farmertec carb to arrive. (I didn't realize I was getting a Farmertec carb until later). If that doesn't work I'll try the brake clean spray to see if there's a leak somewhere.
028 aftermarket carbs are “okay” in that they run better than other series. I’d rebuild that Tillotson proper before leak testing anything. You want a saw that will idle and warm up a bit before the brake cleaner test. Also, those saws have appropriately sized bearings and decent seals that rarely leak (my experience, one never knows). The impulse line is notorious for cracking, though. If that’s been replaced then a carb issue is probably going on.
Yes, but that Tillotson tunes well if working properly. I’ve been into 1118s a few times and didn’t notice a difference in the wood. These saws aren’t screamers like the 026… tune em right (solid four stroke out of wood), replace the air filter that’s usually losing its flocking, and don’t run much more than a 16” .325 combo in hardwood.
I think I have a spare impulse line. I will check the old one for leaks first. My 028 came with an 18" / .325" combo and that seems to work pretty well so that's what I ordered for my buddy (oregon versacut + powercut chain). Thank you. I've ordered a rebuild kit for this carb so if the Farmertec one doesn't pan out, I'll use this. And if it does pan out, then I have a spare carb which isn't the worse thing in the world either for an additional $16.
Here's a link to the the Tillotson site for all the gasket and rebuild kits for the HU model carb. https://tillotson.ie/wp-content/uploads/2016/08/HU-Repair-Kits.pdf And here's a link to all their models. Carburetor to Kit Cross Reference - Tillotson
The aftermarket carb seems to be doing ok although I needed to turn out the screws a little more than I'm used to. Got the saw idling and running pretty good today. At first it was dying in the cut so I richened up the H screw a bit to give it some more gas and that seemed to do the trick. Had to do that a few times a little turn at a time and then it was really cutting well. Everything working as expected. Got a load of ash from one neighbor and another wood chopping neighbor saw me out there and asked if I could take some spruce that he was unable to split by hand that was given to him by yet another neighbor right there. So I took two truckloads home today and it was perfect timing as I had completely run out of rounds to play with.
