Engine switch

[Deleted User]

I have a 1979 Spitfire with a good engine but a bad body, but I also have a 1981 Spitfire in great condition and would like to switch them. However, I found out they used different engines. My question will the Kohler engine work in the 1981 sled? I see the wiring all different and has a different carb. Also I have a 340 Trailfire engine and was wondering if that would fit in the 1981 sled? Please let me know. Thanks

[Liquifire 4/6]

You can switch them no problem at all. You'll need to use the 1979 exhaust manifold and pipe extension (the muffler itself is identical on both sleds) and possibly the base plate as well, in order to mount the Kohler into the 81 chassis. The carbs should be identical aside from the Kohler running a slightly different main jet (I think the Kohler had a main jet one size richer than the Kawasaki). If the carbs are different as you state, there are two possibilities 1) Someone has changed the carb on one of the sleds to a different type. 2)The sled you think is a 1979 might actually be a 1978 in which case, it would have a different carb...a Mikuni slide valve, instead of the Mikuni butterfly that was used on all 79-82 Spits. In any case, just use the original carb that was on the Kohler and you should be fine. If it was a slide valve, you'll need to use the original airbox-carb rubber grommet as well as the original throttle cable and choke set up. The wiring connector is a bit different between the Kohler and Kawasaki engined sleds, but it's pretty straightforward to figure out how to splice it in. I'd walk you through it if I could remember the exact procedure, however I do not, nor do I have any Spits kicking around to look at and figure it out. In my opinion, the Kohler engine worked a bit better in the Spitfire...I think the horsepower rating was identical between the Kohler and Kawi, but the Kohler seemed like a torquier mill to me and those direct drive sleds certainly do benefit by having a wee bit more torque at low RPM's. The only downside to the swap is that the CDI boxes on the Kohlers, generally were not as long lived as the rest of the engine and if you ever need to replace yours, you may find it difficult (& costly) to find a replacement...whereas the Kawasaki CDI's seldom fail and if they do, they are relatively easy to find (& cheap). Hopefully yours will continue to kick out spark for a few years to come. Have fun with the swap.

Pete

[Liquifire 4/6]

While typing my response, I completely forgot about your question regarding installing the Trailfire engine into your Spit. I would not go as far as saying it could not be done, but it would be considerably more work. It would likely entail butchering the hood to make the engine fit which is something I would not want to do. Furthermore, you'll run into all kinds of obstacles you'll have to work around such as figuring out the clutching, mounting an exhaust (the Trailfire exhaust system simply will not fit in a Spitfire.....will the Spitfire exhaust work well on a Trailfire engine? I doubt it). You may also find that the carb sits at a different angle which may contribute to the installation difficulties (I'm not certain that it would be an issue, but I suspect it might be). Also, the engine bay of the Spit is designed with a F/A engine in mind and stuffing a fan cooled mill into it would likely be a bit of a nightmare forcing you to be creative in designing some homemade ducting. So possible? Yes. Easy? No.

Pete

[Spitfireguy]

iv done it. i put my 78 kohler in my 80 body. took me bout half a day and eveything was done and it worked beautifuly. fast sleds.