Need mechanical help

[Toad Harbor Club]

Finally got my restored 1965 model 444 on the snow. Was a real blast but need some help to get the machine running properly

Starts easy and runs well at low to medium throttle. Dies out quickly though when approaching full throttle. Will run at close to top rpm for a few seconds then quickly dies back down to a lower rpm. I can manage to keep the engine running (it recovers) and the cycle repeats itself over again when I attempt to go faster. I can maintain steady low to medium rpms without trouble.

I replaced the fuel lines with transparent hose and can see no air locks forming while underway. Verified the gas cap is vented. I monkeyed with the carb low speed jet setting, runs best at 3/4 open as the manual suggests. High speed jet is "fixed" - just has a screwed in brass plug. I checked all the screws on the carb for tightness and it all looks good. I do not believe I have rust build up in the tank or that the fuel valve is blocked.

I rebuilt the carb this summer, but it runs well at all rpms except full so hopefully that is not the problem. I put in a new coil and condensor as well. Not sure if I have a fuel or electric problem.....

I doubt if the problem is as easy as trying a different spark plug - the manual recommends a champion K 13. My local parts store sold me an autolite 388 plug which is supposed to be the equivalent. Some search on the internet suggest trying a NGK A-6 as the best cross referenced plug. What is everyone else using? This has the 10.4 hp JLO motor.

Any suggestions are appreciated - sure is a lot of fun running this machine and my family and I are getting quite a kick out of it.

[Barrie2777]

I am sure this is a fuel problem. The last Diablo problem was an air leak. The engine would only run if the choke was on thus creating a richer mixture to compensate for the air leak. Yours is different because it runs well at low and mid rpm but coughs at high rpm. I would check the fuel valve first. At low to moderate rpm it may be able to suck the gas through a blockage but at the higher demands of high rpm, not enough gas gets through. The same goes for the screen on the top of the carb...make sure it is not partially plugged. What color is the plug when you remove it?

[Toad Harbor Club]

Thanks Barrie - I'll check the fuel supply as soon as I get a chance. The carb screen looks unobstructed. The plug color is a dark brown (a lighter brown is the end goal I believe....)

Couple of other items that I could us help on (and maybe other folks as well)

How tight do you adjust the tracks? I installed new tracks this summer (belting, wood cleats and steel channel) and they are exhibiting some break in "stretch". Initially I had them too loose and the steel cleets would "bang" the underside of the fender.....

How tight do you adjust the drive chain? I installed a new chain and adjusted to about a half inch deflection. I'm using gear oil occasionally for lubrication (is that a good idea?)

When charging through the deep white stuff, snow packs in around brake and general interior of the hood cover. Thinking of blocking off the screened area around the headlight - using rubber matting maybe? other ideas? Would this cause engine over heating?

Thanks for any insights on fine tuning the 45 year old snow monster

[Barrie2777]

Your tracks should "hang" down some, fiddlestring tight is no good. When you push the machine on the floor, the tracks should roll rather than slide across the floor. You could be a little tighter on the chain but some loose is good. Gear oil for lubrication is a good idea. Snow in the engine compartment is ok as long as the engine is running well but perhaps this snow is leading to your engine trouble???? Why don't you block it off with cardboard,rubber, scotch tape, anything just to see if there is a relation to the snow and engine performance. Is there a cover on your carb intake?

[fap67]

When I bought my 444, the hood scoop and half of the grill (the side with the brake) were filled in with sheetmetal. It still got quite a bit of snow build up under the hood. When I restored it, I put the expanded metal back in both the hoodscoop and grill but I put a rubber snowflap off the front of the fender as you can see in the photo. With the snowflap, I don't get the snow coming over the hood and getting in my face like it used to. I don't get any snow coming in the hood scoop and packing in by the carb. I get very little to no snow under the hood on the side with the clutch. I still get a lot of snow under the hood on the side with the brake. I think the fan is sucking in the fine snow dust and causing it to settle on this side of the engine compartment. So far, I've put over 70 miles on it using a gps as an odometer, so its been tested although the snow isn't very deep yet.

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[Toad Harbor Club]

Thanks - I think I will copy your design ideas.

By the way - your machine looks fantastic, great job!

[Toad Harbor Club]

Here is some comical resolution that some may enjoy.....

Got some time off from work so I started the day with determination to fix the 'ol 444. Had some black plastic material laying around the garage so I fabricated a nice little cover for the headlight hood vent in hopes of blocking snow into the engine compartment. Next I drained the gas from the tank, ran a wire thru the fuel shut off valve and did my best to remove any material (found just a little gunk). Checked my home made carb intake screen (a home depot sink strainer) and all looks well. Then I filled 'er up with fresh fuel mix, put a "fire" in her and off I go.

Runs decent at first then starts the stalling at high speeds again. Stalling Is more pronounced when ascending an incline......

The whole time I'm driving the machine I think of all the work I did (without any previous experience) and what I probably screwed up - rebuilt carb, replaced electric components and the list goes on and on. To complicate things further, I know that I bought the machine with the engine seized, and parts removed and missing.....so I'm thinking the worst and expecting the need to call in an expert to troubleshoot this thing further.

A moment of inspiration occurs as I motor and bump along the field....problem seems definitely fuel related and is particularly sensitive to inclines....hmmmm

I shut the machine down and check the operation of the butterfly choke. The arm mechanism is loose and the "butterfly flapper" is free to pivot! I tighten everything up so the choke assembly is intact, pull the rip cord and now the old girl is screaming (ok - maybe 20 mph) down the trail! SUCCESS!

Lessons learned - these really are pretty simple machines and sometimes it's just basic things that need to be checked. In a way, Barrie called it correct when he asked if the intake screen was clear (well it sure was not when the vacuum created at higher rpms' caused the butterfly flap to close and flood the engine).

I share my embarrassing story to help any other folks out there who are scratching their heads with mechanical challenges , and to thank the folks that chimed in with helpful suggestions (this is really a great site).

Have a great new years everyone!

[Barrie2777]

Great!! When you know your machine inside out as you do, it is best. Yes , always eliminate the simple before dismantling looking for a bigger problem. How many times have I cranked an engine after replacing the plug and it wouldn't start only to find I had forgotten to reattach the plug wire.