78 Spitfire timing

[skibike69]

I am about to finish assembling a Kohler 340 free air from new old stock parts.

I have a NOS stator coil, assembly to go in and a new aftermarket ignition coil and new aftermarket CDI box.

My question is: How do I set the timing?

The old stator coil assembly appeared to be set close to "zero" on the timing marks. So I figure that is a good starting point, but how do I tweak from there?

New crank, pistons, cylinders, and heads... I really don't wanna burn it down because I set the timing wrong.

Any help and advice is appreciated! Check out a photo of my sled in the "registration" section - I am new to the forum.

[S_Kyle]

Your writeup on the spit fire says you have updated to what looks like a rubber track. Any details on this conversion?

Scott

[Hawkeye]

Skibike, while I don't have even close to the amount of time a lot of guys on here have with these JD sleds, I did recently completely rebuild my 79 Spitfire. I also put in new coils, stator and (2)CDI. I set mine ever so slightly advanced less then 1 degree on initial set up. Once you put it all back together, their is a plug on the stator housing that you can remove and then shoot a timing light and see the flywheel. Mine was right on, so I didn't have to open it back up to change the timing. My guess is that if the timing was way off you then would dis assemble and advance or retard the stator and repeat the process. Others can correct me if I am steering you the wrong way.

This of course was after I purchased a second CDI. LESSON LEARNED HERE: Initially I purchased a Kimpex CDI that was for the 78/79 Spitfire. It was significantly cheaper then all the others ($49), however it never worked, either it was bad out of the box or I believe it is actually not the right unit. My second CDI purchase was a Snow Stuff version ($139), this one not only looked like the old one but worked like a champ. Hopefully others can learn from my lesson.

I too would be interested in understanding your rubber track conversion. If you have pictures and information you could pass along, I think a lot of folks would be interested. Also there are some great Spitfire smart guys over there in MI, hopefully they will share some thoughts as well. Good luck.

[skibike69]

As requested, here are the details of my track conversion... Probably nothing I have done that most of you don't already know:

I purchased a new rubber track from Image Enterprises back in 2000. It was not cheap, probably worth twice as much as the entire sled. At the time, I purchased the second to the last one they had in stock, and I was told that they are no longer available from Kimpex.

The track is a Kimpex #267538 (OEM#04-796)

I am using four of the stock 7 lug sprockets, two of them have been modified (see attached pic).
Stock 8" rear idlers plus two more mounted on the rear cross shaft
Slides re-spaced to align with the track clips (I forget the dimension) using new shafts made from scratch.
New wider rear axle machined from scratch.
Entire skid mounted further back in the tunnel, 1" if I remember correctly?
While I had it apart, I replaced the drive shaft bearings, and cut the original carrier wheels open and installed new bearings.
Oh yeah, I replaced the outer 2 tunnel protectors with Arctic-Cat style plastic protectors over the track clips.

OK, the drive shaft is kinda Swiss-Cheesed with new mounting holes to make all the sprockets line up with the lugs on the new track. Will it eventually break? Probably. Will it move a lightweight rider around for a while using all 25 or so available horsepower? Probably. I ran it for years with only the center drivers installed, and never had a problem, but I was never happy that the track was driven in the center, and the idlers were all the way out on the edges...

You will notice in the pics that I am not running a rear shock. The original froze up, and I have not bothered to replace it yet. Even if I do replace it, I doubt this machine will ever handle the whoop-de-doos like my Ski Doo Rev...

[JDT]

Very nice work you have done. Looks perfect!

[skibike69]

Think snow!

[skibike69]

Update - Motor is finally back in and running. Now I need some more snow so I can test ride and tune.

[ICCSF 108]

Are you going to put Farmall decals on it?

Kenny

[tnc110]

what carb is that? it isn't stock is it?

[skibike69]

what carb is that? it isn't stock is it?

It is a 38mm round slide Mikuni. No, not stock. It was on it when I got it.
Compared to my friend's stock Spitty with a butterfly carb, mine lacks bottom end power, but definitely has more top end... 38mm is probably too large, perhaps a size or two smaller would be ideal, but I don't have carbs & flanges laying around to swap and try.

[S_Kyle]

I would agree, I think a 32 would be a better choice for the motor. The 78's had a VM-25, the snows had a VM-30 and the sprints a VM-32.

[skibike69]

Thanks for the reply, Scott Kyle! I have to believe that you are correct... Maybe some day I will get my hands an a 32 and give it a try.

Just for the record, my sled idles, runs, and rides fine with the 38. So I'm in no hurry to change it.

[S_Kyle]

You could try to bump the pilot jet jet one size and see if that helps the bottom end. But I am with you in if it`s working decent leave it alone. I have been meaning to tune my LF for 3 winters now but it starts and runs great so I have left it with the rich jetting in it.