78 JD spitfire 340 wont rev

[roblarss]

Just got a 78 spitfire 340 and im having some running issues. Biggest issue is I have no clue what was done before me.

Stator was out and dismantled but I reassembled it and it fires up and idles pretty decently. Give it throttle and it just bogs down. I can hold it there and it wont rev up at all. Spits gas out intake. Compression is about 90-92psi per cylinder. It has what im assuming is not the original carb. Mikuni 38mm (measuring intake side). 190 main 25 pilot needle is all the way down. Tried a second CDI that came with it and same issue. left cylinder doesnt fire as much as right but sometimes it does even out. Seems way better when i dropped the needle and let the slide down more. I am wondering if the carb is to big and flooding it out. Choke makes zero difference but I did loosen the adjustment so it seems to be fully closed as I was suspecting it was partially open.

Open to ideas. seems a decent sled for my son to drive around yard.

 

[snopro]

Could be a carb blockage but 38mm seems like a big carb for that sled. Did you look at main jets and pilot jets? Could be plugged from sitting

 

[sledneck__11]

On my spitfire the primary had seized and wouldnt shift in snd then would pull the motor down

 

[roblarss]

Could be a carb blockage but 38mm seems like a big carb for that sled. Did you look at main jets and pilot jets? Could be plugged from sitting

I cleaned the carb out pretty thoroughly. Was full of green crap. Jets are nice and clean now.

 

[roblarss]

Nothing changed with the belt off. Still idles alright but spits out the carb and does nothing but change sound when throttle is given. Tried to give fuel from bottle and also cover part of the intake with hand to see if I can find the magical formula to get some more RPMs out of it.

I wonder if it could be an issue with crank seals so its not pulling the fuel in? I cant see the stator timing being off affecting it this much. I just put the stator in the middle which is where it looks like the bolts used to be. Pulled the primary outer sheeve off but cant get the inner off to check that side. Seems to use the same removal bolt as my summit but I have alot of pressure on it and some heat.

Sprayed some cleaner around the seal behind primary and it didnt seem to change anything.

 

[snopro]

Nothing changed with the belt off. Still idles alright but spits out the carb and does nothing but change sound when throttle is given. Tried to give fuel from bottle and also cover part of the intake with hand to see if I can find the magical formula to get some more RPMs out of it.

I wonder if it could be an issue with crank seals so its not pulling the fuel in? I cant see the stator timing being off affecting it this much. I just put the stator in the middle which is where it looks like the bolts used to be. Pulled the primary outer sheeve off but cant get the inner off to check that side. Seems to use the same removal bolt as my summit but I have alot of pressure on it and some heat.

Sprayed some cleaner around the seal behind primary and it didnt seem to change anything.

As in ether or brake kleen? Ether will tell you if you have a leaky seal. Stator is probably in the wrong spot and timing is off if that’s how they time those things. I do t know much about them other than riding a JDX 4 as a kid. Try and find some info on timing for them on Google. Your local Deere dealer may have some old shop manuals in storage as well?

 

[roblarss]

I sprayed it with brake cleaner.
May have just found something. An old kohler service manual says to use a timing light to set timing. If #1 is truly the PTO side (as shown in one of the manuals) then the engine is 180 degrees out. Seems strange. Wouldnt think it would even run that way. Which side is 1 prob doesnt matter as both sides spark every rotation. Could also mean my crappy timing light is faulty...

Going to check next with a dial indicator in plug hole and see where the mark is in relation.

 

[snopro]

I sprayed it with brake cleaner.
May have just found something. An old kohler service manual says to use a timing light to set timing. If #1 is truly the PTO side (as shown in one of the manuals) then the engine is 180 degrees out. Seems strange. Wouldnt think it would even run that way. Which side is 1 prob doesnt matter as both sides spark every rotation. Could also mean my crappy timing light is faulty...

Going to check next with a dial indicator in plug hole and see where the mark is in relation.

Never heard anyone use brake kleen to check for air leaks. We’ve always used Ether

 

[roblarss]

Never heard anyone use brake kleen to check for air leaks. We’ve always used Ether

i would use ether but all out currently. Figured the brake clean burns so it should work.

 

[roblarss]

Got it figured. Moved the timing adjustment all the way and off it went. Timing marks arent even close on the stator. Must have a different backing plate or something. 8 year old is making tracks around the yard now.

 

[snopro]

Got it figured. Moved the timing adjustment all the way and off it went. Timing marks arent even close on the stator. Must have a different backing plate or something. 8 year old is making tracks around the yard now.

Enjoy! Those were one of the coolest sleds ever built.

 

[roblarss]

Well it was short lived. He got about 10000km driving around the yard. Was not running as great today and then i went to start it and it acts how it did before i cranked the timing i think as far advanced as i can. I wonder if the stator still has an issue. Anyone have a spare stator? Ebay has some but will take a month. Or a reliable place to rewind one around red deer or Edmonton. Sled did run amazing but earlier today it seemed sluggish at top end. Now it just idles and wont do anything when i hit throttle.