JLO/Tillotson HR not running so well..

[elwesso]

So in my other thread, I was chasing down an intermittent spark issue which turned out to be the simplest thing of all- the spark plug..

So I got the engine started, once I replaced the plug it started nearly the first pull.

The problem now is that the engine will not run for very long and to keep it running I have to feather the choke, with it wanting to err more on the side of "on", or the choke butterfly in the closed position..

This is a tillotson HR carb, I recently bought a rebuild kit and replaced the diaphragm, needles, and basically everything else that comes in the kit... The screen was cleaned good too..

The fuel is brand new, mixed roughly 20:1.. It seems like its getting good fuel, because when it is running there is a nice stream of fuel coming out of the return line. Not a huge amount, but enough to know that nothing is clogged, which leads me to believe that the fuel filter is probably not clogged. I have not replaced the fuel filter.

What do you guys think I should look for?

[Robinhood02]

first thing i would check is the fuel pump ,make sure that the 3rd line (that goes to the cranck-case) is in good shape and not leaking air due to cracks ,if it is in bad shape it will not operate the fuel pump diaphram properly, if all is well with fuel supply then the next guess is float level (concidering you just replaced the carb parts) be sure the float isn't closing prematurly and starving the engine , and 3rdly i would double check the flow control galleys in the carb, if you had sludge and wax in the float bowl then it is likely you didn't get the galleys cleaned completely (an air compressor will usually blow them out OK with a good rubber tip on the blowgun)

[elwesso]

Thanks for your reply.. I'll replace that hose going to the crank case just in case, seemed like it was in OK shape but it would be a good idea to rule it out..

When you say the float, what are you referring to? Are you referring to the little lever that sits on top of the inlet needle?

do you think it could have anything to do with the fuel return being below the gas tank? for clarity, I put in a new fuel tank, but I have not yet put the return line in the tank, I had the return line going into a jar on the floor

I also did not remove the 2 welch plugs up in the carb, the carb did not seem that dirty when I took it apart so I skipped that part.. I sprayed everything down very liberally with carb/choke cleaner..

[hydromike]

Hey Elwesso,

Your Tilly HR won't have a float bowl on it, but if you've taken it all apart and cleaned it, there are a couple other things you can try. You said you're getting sufficient fuel at the carb, based on the fact that there's fuel heading back in the return line. If you still need to have the choke on, there's a chance that the engine is sucking in air past the crankcase seals, or around the intake manifold/carburetor flange. With the engine running, spray a little starting fluid around the PTO side of the crankshaft. The magneto (pull start) side is a bit more difficult, but if you have electric start, you can get in there with the recoil taken off.

If you have a leaky seal, the engine RPM will tend to increase as it sucks in the starting fluid. If this is the case, you'll need to strip it down and replace the seals. It's not all that difficult, but you will finally need to pull that flywheel off. Tillotsons have a notoriety for being a bit tempermental, and difficult to keep in a good state of tune on small two strokes. If there's any chance you could upgrade to a small (30mm) Mikuni carburetor, it would likely be a big improvement. If your seals are bad, the Mikuni won't do a thing to help, but it's a good upgrade nevertheless.

Start there, and see what happens...
Good luck...

~m

[elwesso]

I got a chance to look at this again last night.. This stupid thing is driving me crazy!

Engine started pretty easy (first pull actually), and it was the same story as before, you would feather the choke to keep it running.. I played with the adjustments on the carb a bit, and I don't think it made a noticeable difference...

When the engine would die, I noticed that the return line had quite a few bubbles, like air was getting in the system somehow.. I also noticed that the final time I started it and it died, it seemed like fuel was leaking out around the flange where the carb mounts to the engine.. I tipped the carb up a little bit, and a bit of fuel came dripping out.. that is clearly not supposed to happen..

I cant tell exactly where it is leaking.. in any event, I took the carb off and I'll have another look inside it soon..


Ive taken the spark plug off a few times after its ran, and its looked anything from wet to almost running lean.. Its obviously not getting a consistent supply of fuel into the engine..


From what I understand the engine will barely run if the crank seals are bad? When it runs, it seems like it runs OK.. If I sit there and feather the choke and throttle, it will rev up pretty good.. It seems like whatever is wrong is probably in the carb..

I appreciate any suggestions. I should be tearing into the carb this weekend sometime and double checking my work in there...

[jerseybigfoot]

Some pointers on Tillotson carbs:
The Tillotson carbs need to have the gaskets in the correct order to work properly.
The main jet is under the welch plug and has a small spring loaded check that may be may be gummed up and stuck. The rebuild kit should have a small button size replacement disk that allows you to inspect and clean the main jet.
There are a couple of HR manuals on line that are very good.
Tillotson HR

http://www.tillotson.ie/docs/techinfo_HR_US.pdf

[elwesso]

I'm pretty sure i installed the gaskets in the right order but I'll check everything again. I did not take the welch plugs out and go under there, the whole carb didn't look bad. Do you think that could cause an
Issue? I wonder if I could get 2 new plugs it would really suck to buy a whole kit just for those 2 plugs

[elwesso]

I thought I would follow up on this. Turns out I was using the wrong spring under the inlet needle. When I was doing the rebuild, I knocked off some of the parts off the table I was working on. I remember there being a handful of springs in the kit, and I didn't notice which one was the proper one and there was only 1 I could find.. Fortunately, I had an extra tillotson HR carb from my other MAX, so I took the spring out of that, and it started and idled great. After a few mins of adjusting the idle mixture and speed, I have a nice solid idle and it revs up pretty nicely..

My symptoms were that when it would start, it would not idle without messing with the choke, and it was pretty much a struggle to keep it running, even though when it was running it sounded like it was running relatively decent. Basically when it died out it sounded like it was running out of gas, because it would idle good for maybe 20 seconds, and then just die off like it had no gas..

The cause of this was the spring under the inlet needle was too stiff and not allowing the inlet needle to open up properly, so once the new spring went in everything was great..

[hydromike]

Fantastic.... glad you got it figured out. Now go have fun!

~m

[ryangude]

Im having the same issues. with my tilletson carb HR30A this threat was alot of help!!!!!!!! thanks guys, and jersey bigfoot, thanks for the links to the tilletson pages, very helpful and saved alot of time from research, i will begin cleaning my carb tomorrow, any good placed to buy the rebuild kit from? thanks for the help