Tillotson Carb Talk

[JohnnyBlade]

Sounds like the needle is not sealing to its seat, worn seat or dirt on the seat. Need to look at the bore and seat with some light and magnification.

Agreed. I did that and blasted it with carb cleaner and air numerous times. Same results. 7psi. Will the weight of the needle itself hold 15psi or do u need down force from the lever and spring? This is the first time this has happened to me so im full of questions. Every other carb kit i just swap out and it works. Guess i never paid that close of attn before.

 

[Basher]

The carb needs to be wet, have fuel in the metering chamber , then just the regular spring and metering lever will cause the needle to seal. If the metering diaphragm is stiff it will hold the needle off its seat, if the diaphragm has an improper metal contact tip on it, where it sits on the metering lever this will also keep the needle off its seat. AM kits have shown up that have too long of a tip and will not work no matter how the lever is adjusted.

 

[Basher]

I know I can go on about carbs all day, have been into them for more than 55 years now and have seen many maladies with them. The worn seat thing comes up frequently with older carbs along with worn shafts and leaking governors. I have successfully reseated a few worn needle seats on Tillotson carbs using tooth paste and a donor metering needle. Apply the paste to the needle seat and rotate a metal donor needle back and forth like we always did seating valves in 4 strokers. Some older Tillies are hard to replace so fiddling with them becomes a necessity. Much easier to just replace a carb if a new one can be found.

 

[JohnnyBlade]

The carb needs to be wet, have fuel in the metering chamber , then just the regular spring and metering lever will cause the needle to seal. If the metering diaphragm is stiff it will hold the needle off its seat, if the diaphragm has an improper metal contact tip on it, where it sits on the metering lever this will also keep the needle off its seat. AM kits have shown up that have too long of a tip and will not work no matter how the lever is adjusted.

Good info! This is happening with the new and old needle. Both rubber tipped. Is there a standard for metering lever height? Some carbs r level with the body as a standards. The HS250 has a recessed carb body. Should the metering lever be flush with the inside body?

 

[Basher]

Flush with the floor of the metering chamber on the HS series of carb.

 

[JohnnyBlade]

I know I can go on about carbs all day, have been into them for more than 55 years now and have seen many maladies with them. The worn seat thing comes up frequently with older carbs along with worn shafts and leaking governors. I have successfully reseated a few worn needle seats on Tillotson carbs using tooth paste and a donor metering needle. Apply the paste to the needle seat and rotate a metal donor needle back and forth like we always did seating valves in 4 strokers. Some older Tillies are hard to replace so fiddling with them becomes a necessity. Much easier to just replace a carb if a new one can be found.

The more i/ we can learn the better. I thought about the actually carb seat being bad. That would suck! Lets say the carb was left how it is at 7psi pop off pressure. Would the saw still run? Would it pull to much fuel and flood out? Is it an actual problem? Am i over thinking it?

 

[Basher]

Can you post a pic of the tip on the metering diaphragm? There is two different diaphragm types and they need matching metering levers, you may have the two mixed in causing a mis match.

 

[Basher]

The more i/ we can learn the better. I thought about the actually carb seat being bad. That would suck! Lets say the carb was left how it is at 7psi pop off pressure. Would the saw still run? Would it pull to much fuel and flood out? Is it an actual problem? Am i over thinking it?

It would likely run, possibly run a bit too rich and possibly flood a bit but maybe just try it as is, may surprise everyone.

 

[cus_deluxe]

i started messing with an hs trying to get it to run alcohol. after drilling the seat it wouldnt reseal at all, like at all. i cut the cotton off the end of a qtip, tapered the end with a pair of scissors, chucked it in a cordless drill and put a dab of valve grinding compound on it and spun the hell out of it. after about 5-10 mins of that i was able to get it to reseal almost 100%. maybe not the recommended method, but it did work.

 

[Basher]

i started messing with an hs trying to get it to run alcohol. after drilling the seat it wouldnt reseal at all, like at all. i cut the cotton off the end of a qtip, tapered the end with a pair of scissors, chucked it in a cordless drill and put a dab of valve grinding compound on it and spun the hell out of it. after about 5-10 mins of that i was able to get it to reseal almost 100%. maybe not the recommended method, but it did work.

I did use valve grinding compound on two very worn seats but I didn`t have enough patience to get it completely cut down well enough to seal up again. I kept an old tube of the white Colgate in the drawer, it is fairly gritty and will polish aluminum fairly well, I wouldn`t hesitate to use the fine grade of valve compound , still have a near full can left from my old days of cylinder head work.

 

[Basher]

I never could get the plastic module of the HK carbs to re seat , seems nothing works on that type of setup, just replace the module is all that has worked for me. The old HL series of carbs were the best, they could be rebuilt for about ever, replaceable needle and seat barrel was a good idea.

 

[Stump Shot]

@JohnnyBlade The inlet needle is not the only source for a leak, could be the fuel pump side. Dunk in a glass jar of water hooked up to your pressure tester and see just where the bubbles are leaking from to point you in the right direction as to what is in need of repair.

 

[JohnnyBlade]

Just got home fellas. Ill get started in a lil bit trouble shooting again

 

[cus_deluxe]

bumps

 

[Basher]

 

[StuntCockWelder]

@JohnnyBlade = SLACKER!!!!

 

[JohnnyBlade]

LMAO! Forgot i had to get all my taxes stuff ready friday and tax mans Saturday. Not any saw time for me this weekend. Hell i have not even been on the site. Sad times. Hoping to pick back ur tomorrow on the carb dilemma.

 

[StuntCockWelder]

LMAO! Forgot i had to get all my taxes stuff ready friday and tax mans Saturday. Not any saw time for me this weekend. Hell i have not even been on the site. Sad times. Hoping to pick back ur tomorrow on the carb dilemma.

 

[beaglebriar]

Something to try that has worked well for me on motorcycle/ATV carbs that have float needle sealing issues: remove the needle (obviously) then take a small wad of OOO steel wool and stick it in seat. Find a little tool to spin it with. Small straight blade screwdriver works good in a ATV/MC carb but you may need to find a tool that's smaller or grind one down. Be careful not to scratch the seat, the steel wool will remove any varnish or corrosion that may have formed in the seat. You don't need to go crazy, just a little bit of polishing usually does the trick....if that's indeed the issue. A little shot of compressed air will pop the steel wool out if it gets stuck.

 

[JohnnyBlade]

Carbs out. Here we go again.