Husky 51 won't stay running

[eriklane]

Having an issue with a 51 that I bought off ebay with a blown cylinder. Put a 'big bore' cylinder on it. Will start when choked but races then dies. Is it possible that the big bore cylinder requires a carb or timing change?

Been through the carb twice, cylinder gasket good, appears to have no leaks. Has great compression. Fuel filter very clean (saw is newish).

 

[Sprintcar]

Pressure and vacuum test will answer your concern. Check for leaks on both crank seals.

 

[eriklane]

I was trying to vac test but didn't have time. Will do that.

 

[cus_deluxe]

A common failure point on those is the intake “bulkhead” and pulse grommet that sticks in the cylinder. Easy to strip the threads in the plastic and the grommet deteriorates over time

 

[eriklane]

You might explain more, as i've never head of an intake bulkhead lol. But the pulse grommet (round black seal) I need to double check. What happens there? leak?

 

[Ozhoo]

This impulse grommet is a rubber piece that fits into the impulse port on the cylinder. Take a gander at this.... the bulkhead is plastic and after the carb has been removed and installed a few times, the screws no longer hold the carb tight against the bulkhead.

 

[eriklane]

gotcha, yeah I do have the intake gasket between the carb and the bulkead and that's in good shape, and my rubber intake gasket between the jun and bulkhead is good, so I will check that grommet. Good catch. Typical me, going into full disassembly mode (checked jug gasket last night lol), and it may be that dang grommet...thanks.

Note to others, I had a small Stihl once that wouldn't start, the air cleaner (former owner) was so gunked up it couldn't breathe...blew it clean, bam.

 

[s sidewall]

Definitely check the carb to cylinder head manifold, they do crack over time. I did the so called big bore a few years back on a 51, 55 top end. Didn't have to really change carb setting much. Top end was toasted on the original because intake was cracked and impulse tube wasn't sealing up.

Steve

 

[eriklane]

OZHOO-turns out the impulse grommet was in the old cylinder. I don't work with these much so I didn't even realize it was there, and when I put the bulkhead in, I just figured it fit into the hole snugly...So I put it on, and the saw didn't start. Will try tonight with some starting fluid, but I think it's not going to run. Getting fuel, checked that. So has to be a big air leak or carb.

I've never pulled welch plugs, don't have the tool. Is that necessary to check for gunk?

 

[s sidewall]

I've seen crude built up behind them, tiny holes behind them. Drill a tiny hole in the middle, not deep, to the point the drill bit just make a small hole. Then pop it out with a small pick.

Steve

 

[grizz55chev]

OZHOO-turns out the impulse grommet was in the old cylinder. I don't work with these much so I didn't even realize it was there, and when I put the bulkhead in, I just figured it fit into the hole snugly...So I put it on, and the saw didn't start. Will try tonight with some starting fluid, but I think it's not going to run. Getting fuel, checked that. So has to be a big air leak or carb.

I've never pulled welch plugs, don't have the tool. Is that necessary to check for gunk?

No starting fluid, mix gas only! Blown cylinder means you had a problem before, a vacuum test is needed before proceeding further.

 

[eriklane]

Yeah, it won't start, tried last night. I have a Mityvac but it's suction, not pressure, so I needa figure out how to test everything for leaks.

 

[Wood Doctor]

My Husky 51 upgrade went OK (knock on wood), but I had similar symptoms with a Husky 350 that you are reporting here. I eventually installed a new carb and the engine ran OK after that. However, it still does not come close to the Husky 51 in power. The 353 does, even though it weighs less, and I guard it with my life.

 

[Tomas Caballero]

OZHOO-turns out the impulse grommet was in the old cylinder. I don't work with these much so I didn't even realize it was there, and when I put the bulkhead in, I just figured it fit into the hole snugly...So I put it on, and the saw didn't start. Will try tonight with some starting fluid, but I think it's not going to run. Getting fuel, checked that. So has to be a big air leak or carb.

I've never pulled welch plugs, don't have the tool. Is that necessary to check for gunk?

I have one of those plastic pieces of crap from a Husky 51 I worked on for my legal assistant's dad. I bought it but never installed it because I heated some threaded inserts and melted them into the plastic piece of crap. Then epoxied and saw still runs after 5 years. I will post a pic.

 

[Tomas Caballero]

Is this it? Baby the three legged chihuahua thinks it is. Part no. 503 76 48-01. Says Partition on label. You can have it for postage.

 

[eriklane]

Turns out I had the cover on the carb not on right DUH. Now it runs but wants to die out low and is rich. Might need some tuning but it runs.

 

[Wood Doctor]

Turns out I had the cover on the carb not on right DUH. Now it runs but wants to die out low and is rich. Might need some tuning but it runs.

Close the low speed setscrew a tad and perhaps raise the idle a tad. You should be good to go.

 

[eriklane]

I did fiddle with the screws and got it going finally, thanks guys.

 

[grizz55chev]

I did fiddle with the screws and got it going finally, thanks guys.