73 JD400 with Tillotson HD107A

[Corey JD400]

Hey Guys

I'm new to this site and looking for some help with my sled. I bought my sled years ago and it has never ran/idled correctly. I never realised that the carb on my sled wasn't the stock carb. Someone replaced the WDA-32 with a HD107A from a 73 TNT 340. They look so similar except for the round vs square bottom end. Currently, the sled will start with the choke closed, rev high then drop off. If I get on the gas I can keep it going and drive but never a solid idle. Here is what I have done to-date: new gas lines, new Winderosa carb kit, fresh gas mixed at 50:1, rebuilt the engine, crank seals, new plugs, repaired the stator, new points. I guess there's a few answers I'm looking for:

1) I was just reading an old manual today that said the WDA-32 must have the silencer on it to run correctly. I have never had one and wonder if its the same for the Tillotson as it will spit gas as I read the WDA32 will do. Should I get the silencer and should that fix the issue?

2) Is the HD107A even a compatible carb to use on the sled? It measures 44mm at the opening...

3) Should I it get the silencer and maybe redo the carb again? (basically keep putting time/money into the HD) Or do I order the Mikuni 34mm and swap it out? Also, if I got the Mikuni would the VM34 be the right carb?

I've read a lot of for/against on the Tillotson carbs so I'm sure I'll get a mix bunch of answers.

Thanks everyone!

[Matt]

I would clean the carb again. Soak in carb cleaner, then blow out the passages with compressed air. Look at all the jets and passages very closely. The silencer is supposed to help with air pressure but wouldn't be the cause of your problem, it would still run without it.

[Corey JD400]

Thanks Matt

I'll give it another run. All the guts of it have been cleaned and replaced many times. For the age of it, it's sparkling clean.