C77 Fouling plugs

DianneB · Post by **DianneB** » Wed Jun 28, 2017 3:44 pm

The C77 that I rebuild a couple of years ago is "eating spark plugs"! :(

They get fouled after a few hours running and then stop sparking.

The plug on the left has a few hours run time and the one on the right less than an hour.

I presume it is running rich but I can't find anything in the manual about how to set the C-clips on the throttle needle. I started with the "recommended position" and moved the clips down once but taking the carb off of a C77 is a PTA! How do I know when I have gone too far or do I have to do it one notch at a time?

DianneB · Post by **DianneB** » Wed Jun 28, 2017 3:47 pm

Can't attach picture - get whole list of error messages!

G-Man · Post by **G-Man** » Wed Jun 28, 2017 3:53 pm

To make the mid-range leaner you need to move the clip up the needle. This drops the needle lower into the jet.

You may have the float height set too high or a leaky float valve allowing the fuel to sit too high in the chamber.

If it is running rich on wide open throttle you may need a smaller main jet.

G

DianneB wrote:Can't attach picture - get whole list of error messages!

DianneB · Post by **DianneB** » Mon Jul 24, 2017 3:44 pm

Finally had a chance to get back to "the Purple Dream" ad pull the carb off - PITA job!!

The clip on the needle is all the way to the top and the main jet is marked "120".

I had bought a carb from a salvage yard as a spare that had come off a running bike so I opened it up to compare the two. On the needle in the spare carb , the clip is in the 3rd ring from the bottom but the needle appears to be slightly larger in diameter and have a more blunt taper. (I should mic both before I putt hem back together!) The spare carb also has a 120 main jet.

I am wondering if the needle from the overhaul kit that I installed in the first carb might be the wrong size.

I HATE the frame design of the 305 Dream - so bloody hard to put the carb on and take it off! And to get the 'air tube' from the cleaner on to the carb is a ROYAL #### PAIN! No wonder they went to a tubular frame with the next model!

Muddy · Post by **Muddy** » Tue Jul 25, 2017 4:12 am

Very sincere sympathies to you, as I know the pain you're feeling. I chased a rich carb and fouling plugs around and around many times - in the end I could get that carb off very efficiently.

In the end I gave up on the carb I had (to be further investigated at a later date) and put a cleaned, second-hand genuine carb back on mine. I noticed the difference immediately and the plugs appear to have cleaned right up. Something about the float level or float in the original one I reckon is the problem.

There are reports of several after-market kits out there sold as suitable for for our bikes but with incorrect parts for our carbs. You may have scored an incorrect needle. Others would know for sure, but a larger diameter needle in the same jet would indicate less fuel and be leaner. Make sure the float level is right before going any further. Lower the fuel level in the bowl a little at a time to try and lean things out a little.

The other thing to do, as LM always says is check the valve timing and the ignition timing first - these always have to be correct to get the carb right.

Good luck and by the way I love that "Purple Dream"!