help ? Engine or carb options for an Attex 300 ( Jlo 297 )

[swfleur]

Carb issue with Tillotson HR 31 A

Hello Amphibs

See photos and please comment - My carb is still giving me trouble - Attached photos show it installed - I rebuilt it more than once - new welch plugs, needles, seat, seals, - adjusted the high and low screws at several suggested turns and did what the factory setting shows - . I'm reading that some models had 2 gas lines - 1 for feeding - 1 for return - this has only 1 fuel line for supply - into bottom bowl - The trouble is - cant get it to suck fuel long enough to run - I can start it - I can rev it but I have to work the choke to make it keep running - doesnt want to Idle and when I go wide open - it only runs a short while and craps out - OMG i want to bash this tilly with a hammer - cleaned the pulse port - dont seem to have any leaks - I may yank the whole engine or replace just the carb - I have posted this before but added more info and pics this time - thanks all and please feel free to tell hey ... " hey dummy - did you check the ______? " I'm leaning towards another carb or more beers while working on it

[teeko]

More beers never hurts. I'd say that is a good place to start. If you youtube a user named ishobie ( I think) or isahobie he has a very detailed video on rebuilding a tilly. Did you but a rebuild kit? I had bad luck when I installed the supplied mixture screws. I had to go back to the old ones and it works fine. Many people have made the switch to a Mikuni with good results. If you just cleaned it you may need new diaphrams which come with the kit. There are also some little check valves in the carb, one under the welch plug. Shake the carb to make sure this is rattling, or free moving. It may be stuck. Also, Hey dummy, did you check the supply line for crap or blockages? No offense! Change your filter too. There are about 3 bucks if you haven't already. Hope this helps.

[Bazooo guy]

In the first pic there is a small brass fitting on the top of the carb near the engine.
Is it plugged?
If yes remove the plug and see if fuel comes out the fitting when the engine is running.
If no fuel comes out the fitting plug it with a rubber cap.
I think its for a primer tube that would connect to the fuel line.
The needle nearest to the engine should be around 1 turn open to start.

[swfleur]

Teeko - Yes - I had to reuse the old screws too - the new ones in my rebuild kit were crap quality - I did in fact replace the fuel filter and I'm sure I have good fuel flow to the carb.

Bazoo - the brass barb is for priming - it's plugged very well- no fuel comes out of it when I unplug it - the needle nearest the engine has been set from 3/4 to 1 turn - still I despise these tillotson carbs - I would be willing to ship to anyone that can hook it to a JLO and make it work - and ofcourse pay them for the trouble ( which will be alot I'm afraid - trouble

[jpswift1]

I'm going to suggest you get rid of the horribly temperamental Tillotson carburetor and replace it with a Mikuni VM round slide. You'll save yourself lots of headaches. I've been there too. I think a 28mm should work for you.

[Bazooo guy]

Have you done a compression test?
Is the intake gasket leaking? Has the exhaust been modified?
It sounds like its too lean if you need to close the choke to keep it running.
Try opening the needles another 1/2 turn and hold the throttle slightly open to start.
Are you spraying gas into the carb to get it started?
Make sure your gas/oil mix is correct.
Also ... if you are using a pulse from the intake ... do you have inserts that go into the bolt holes on the carb? These inserts help line up the pulse hole of the intake flange to the pulse hole on the carb flange. There is a lot of play if you don't use inserts ... and the holes might not be lined up properly ...

[teeko]

Did you run crappy gas through your machine? Low grade gas especially from a no name gas station may contain higher percentages of ethanol than others. I had this happen to a sled with a tilly. 5 minutes or riding and it just quit. After rebuilding the carb it still didn't run. The intake gaskets were reduced to a tar like goo and it was sucking air. Always run premium fuel from a decent station or marina if close by. Many marinas have no ethanol fuel for this very reason.

[swfleur]

Thanks guys


Singing a song in my head now -

"Im gonna smash this Tilly
before it drives me silly
it's a big pain in my willy
oh lord how I hate this tilly"

I will look at the inserts / alignment of pulse hole - no leaking intake - I dont have to spray the gas - I can choke it and make it start -but It wont stay running with the choke on - it floods - therefore I have to unchoke it and then it stalls anyway - i can sometimes find a sweet spot after starting it to keep it just slightly choked choke but that isnt consistent

I have replaced all gas with good new mix - no ethanol - good point there -


Who wants a free Tilly carb
I'm gonna give it to Barb
She might get it to sing
but lord how I hate this thing

[swfleur]

What should the compression be ? I did check it and referenced this site and recall it being ok - I think I had 90 to 120psi - not sure but I wrote it down somewhere

[Bazooo guy]

Is your engine a JLO/Cuyuna L297
I read somwhere the compression ratio was 11 to 1 and they were getting 180psi compression.
Sounds unreal ....maybe they did some mods to the engine.
Try closing the high speed needle and see if it will still run.

[swfleur]

Hello guys - sorry for being out of touch - been working too much - and not on the fun stuff

Anyways - just an update on the carb- you all motivated me to tear into the carb again - I found the inside's coated with a yellow pollen like crap - so i pulled the tank off and put a chain in it and sloshed around some gas in it to knock the scale loose - pulled the chain out and then washed and dried it all out.
I replaced all the hoses and rebuilt and cleaned the carb again - also found that the gasket under the needle seat was torn - Anyways - put all new parts in and adjusted the needle lever for the needle - flush with surface. Put it back on and she fired up
also added 2 fuel filters - one near the tank - one near the carb

adjusted the jet's
Idle approx 1 turn -
main jet approx 1-1/4 to 1-1/2
and took it for a spin

Struggled through the 'which spring do I use for the needle and seat lever - 3 come in the rebuild kit - too stiff and you get no gas to the engine - too loose a spring and it drips and floods the plug - okay find the spring - trim it if needed - I think it's good now - but check the pop off pressure - low psi pump - bike pump will work - got in the range of 10 to 15 psi -
She runs but will starve out - I still have to choke it ?? and once it starts up - seems to be okay but still doesn't run 100 % good - will starve off

Maybe i'm sucking air in somewhere ?? any comments or suggestions

[amphibious drew]

If you think you could be sucking in air, spraying starter fluid around the carb while its running will rev the engine to confirm it. If it doesn't rev, you should be good there.

[Bazooo guy]

Great that you got it to run.... the torn diaphram would keep it from pumping.
Run some sea foam in your gas for a couple tanks and see if it gets any better.
Check the fuel filter after a tank runs thru it and see if it is plugged with crap from the tank.
Fix any leaks or it will suck air.
Is it starving for fuel under load?
If it idles ok open the high speed jet another 1/2 turn and take it for a drive to see if its any better.
Also check the spark plugs to see if its running lean or rich and fine tune the jets.