Topic: 1974 K2 750/4 Project

[Steve Campbell]

Hello all,
I've started work on my old Cafe Racer which has not run for 30 years. The good news is that it started up without too much fuss. The bad news is number 4 cylinder is not firing. I have spark. I'm thinking that the problem must be with number 4 carby. Seems a bit strange though because the other 3 carbs are ok. I've done nothing to the carbs except remove the float chambers and clean them out. They were quite clean really.
The valves are operating normally. I am going to remove number 4 float chamber tomorrow  to check for a stuck needle -  hopefully that will be the issue. If not I'll be back looking for suggestions.

[BenelliSEI]

Needle stuck up in some muck? Any luck?

[Steve Campbell]

Still investigating. Started her up with number 4 plug out. Plug is firing while engine is running. So replaced plug. Fired her up again and she ran momentarily on 4 cylinders but then the throttle cable broke! Just got another cable rigged up so will continue the investigation tomorrow.

[BenelliSEI]

If it doesn’t come alive, try unscrewing the “low speed” / idle jet (the small one). The holes in them are impossibly small and get plugged up. Don’t be tempted to push anything through it, that will damage it. Soak and compressed air until you can see right trough it......

[Steve Campbell]

Thanks, Yes, that will be my next move. I really want to isolate issues before removing engine for a re-build.

[Alan F.]

Tip: When you hear compressed air recommended, that includes the cans of compressed air.

 

[Steve Campbell]

Bike is now running on all 4. Blocked idle jet. Thanks all

[Alan F.]

Steve Wins!!!

[Steve Campbell]

Next issue is to investigate precise source of oil leak between cylinders 2 and 3. I have oil dripping  from between the 3rd and 4th finning up from the base of the block. Block has been painted black so will remove paint in the suspect area and clean spotlessly it the hope that I can isolate the precise source. My hope is that the head gasket has given way and that the oil has found a path of least resistance and made it's way out where it has. As soon as all is cleaned up, I'll do a compression test and see what that reveals - step by step! If the block is
cracked then I am in big trouble.

[newday777]

Next issue is to investigate precise source of oil leak between cylinders 2 and 3. I have oil dripping  from between the 3rd and 4th finning up from the base of the block. Block has been painted black so will remove paint in the suspect area and clean spotlessly it the hope that I can isolate the precise source. My hope is that the head gasket has given way and that the oil has found a path of least resistance and made it's way out where it has. As soon as all is cleaned up, I'll do a compression test and see what that reveals - step by step! If the block is
cracked then I am in big trouble.

Most likely it is the rubber disc pucks under the cam towers covering the head bolts leaking oil from the cam area onto the fins, not the headgasket....

[Steve Campbell]

I have started cleaning up the engine

[Steve Campbell]

Seat base tidied up.

[BoneDigger]

Looks like a fun challenge.  If the oil is originating from between the 3rd and 4th fins from the bottom, it is not the pucks. If it was, the oil would be flowing from between the fins in the head. It sounds like you are describing a leak in the cylinders, and the middle at that.  Is this stock bore, or has it been bored out?  A poor bore job could have compromised one of the cylinders and produced a leak.  However, I suspect you may find the leak coming from between the head and cylinder.  Difficult to see when the cylinders are painted black.  If this is the case, it is a leaky head gasket.

[Steve Campbell]

Thanks for taking an interest - much appreciated. Agree with everything you say and hope that you are right about the head gasket and wrong about the bore. When I bought the bike back in the early 80s it had received the Yoshimura 810 treatment. Bike never gave any trouble and was a really quick, reliable machine. It just got tired over about 10 years and then stopped running and ended up in the shed as life got in the way.
It is very clear where the oil is exiting the engine but impossible to tell if it is coming  from higher up or not. It appears about 30 secs after start up.
I now have the engine out and will do a compression test after cleaning the engine so that it is spotless. It will hopefully be much easier to locate the precise site of the leak with the engine on the bench. I can't run the engine but am hoping that with all the plugs out the starter will spin the engine fast enough to build up sufficient oil pressure.
I wasn't able to do a compression test with engine in the frame as I didn't have a siutable adaptor to get into cylinders 2 and 3.
Step by step . I will get to the bottom of it eventually.

[Steve Campbell]

Thought I'd try something different with the frame. Bike is a cafe racer so have no interest in returning it to original condition.

[Steve Campbell]

Painting done by a mate of mine Amit Kawde I am really lucky to have such a skilled craftsman as a friend

[newday777]

Yes that Yoshi kit was great. I put on in my K6 in 1977, along with a 3/4 race cam and a few other mods. I had a lot of fun with it and have deeply regretted selling the bike in 1983.