GK76 Engine overhaul-What do you recommend?

[rgvsp]

Well apparently they weren't the problem. I'm kind of lost at sea right now on the whole issue.

First thought it was carbs, then moved to coils (everything is sparking fine now) and then thought compression related issue. Well tested the compression again (cold engine) and everything came back at 150PSI.

Carbs are getting fuel as bowls are full of fuel but when I pull the plugs they are pretty damn dry, like it isn't sucking fuel into the engine. That is why I thought it might be compression related.

Choke, full throttle, half throttle, doesn't matter, gives no sign of firing. Mind you, the bike was running fine before I took it apart.

So I'm kind of back to somehow I've screwed something up on the carbs.

[Variablevalves suck]

Well i will put all my money on the pilot system in the carbs mate!

[rgvsp]

I managed to find a way to sidetrack myself and waste more money on this project; I bought a SP or SP2 engine. According to the CDI code it is an SP2. I'll have to see for sure. Anyways, I imagine it means another engine rebuild and then swapping it in with the SP harness, carbs and CDI.

[rgvsp]

My winter project has arrived. A big,BIG, thanks goes out to Chris (Variablevalvessuck) for his help in the whole process.

It is a 1990 GK76 SP2 engine. There are no outwards signs it is other than the different part number on the carb inlets for the 35mm carbs. The seller also had the SP2 CDI so I was confident it was the real deal. SP2's were just SP's but with the standard bikes transmission.

I'll have to decide if I'll rebuild it or just use it for the intake cam and carb inlets. Outwardly it is much better shape than I expected but it has taken a serious hit at some point. One engine mount is cracked and the left side case cover has been welded back together.

Last on the list to transform it, is a set of SP forks. Anyone selling?

[rgvsp]

I got to look at the engine a bit more. Underneath I was encouraged to see very little debris in the oil sump.





I took the head cover off and compared cams. While they are both stamped 33C (SP stuff is usually 33C10) the one in the new engine is stamped with an A and S while this stock one pictured is a D and G, so I guess that is a good sign.

[rgvsp]

It is time to tear it down again. I've collected all the parts necessary to turn it into an SP2, minus the forks (anyone selling a set?). I've also got another Autorimessa exhaust system on the way. This one is complete with the original aluminum muffler. The two CDI's I have are from a 1990 SP and 1990 SP2.


I was most worried about the intake cam. The only thing that identified the donor engine as an SP/SP2 was the CDI and the larger carb boots. I had a mechanic look at it and it is indeed an SP cam. It looked like there was almost a mm difference in the loobs. To identify one without measuring they are stamped with an A and S. Top one in the pic.

[rgvsp]

Got the new Autorimessa system test fitted. This one is absolutely complete with the Autorimessa muffler and full mid pipe. The mid pipe has an odd baffle in the middle of it. Not sure what the idea behind that is.

[rgvsp]

While I have the engine out, I wanted to freshen the paint up. Duplicolor Bumper Coating (Dark Charcoal) is damn near a perfect match. I got the info from a GSXR forum. The guys there claim it is holding up to engine heat. I'm wondering how it will hold up fuel spills.



I hope to get the SP cam in there in the next few weeks. I don't trust myself with the shims so I'll take it to a mechanic.

[donk]

It is a good match I've tried a bit off a test piece after you put me on to it . Did you paint the motor all intact or did you do it while in bits ? Your doing a good job keep it going

[rgvsp]

I took off the easy stuff and then just taped and sprayed the rest intact. It came out pretty good for a do it yourself job. Again, no idea how it will hold up in the long run. I know the PJ1 engine paint I had on there before wasn't worth a shit. Fuel ate right through it.