Brake Light and Vacuum Leak

Finally after almost 10 years of not running and garage kept I finished my project. She runs but still a couple of issues on my '83 XJ750K.

1 the brake light stays on, won't shut off. One of the bulbs blewoutta so I replaced them with dual filament bulbs from the auto parts store. I checked the rear brake to see if I had the brake rod too tight by taking the nut all the way off and nothing, still stayed on. I rebuilt the master cylinder and pretty sure the front brake switch is right. I pulled bake the brake lever and pressed in the switch and no change, did this with the rear brake rod loose and tight. Any ideas?

2 after rebuilding the carbs I have a vacuum leak on the number one carb where it connects to the boot on the head side, carb side seems ok. Any idea how to fix this without taking the carbs off which were a pain to put back on?

Thanks,
Joe

 

Have you got the right bulb. The pegs are offset on my machine.



Are there any splits in the intake boot of your carburettor?

 

Thanks for the reply Franz. The bulbs look the same and the boot is new. When I spray starter fluid at the boot where it touches the intake it seems to smooth out a bit. I'm thinking maybe the gasket is bad but how would I get that off without removing the carbs?

 

If the leak is at the boot cylinder head joint you will have to remove the carburettors. Have the two bolts holding the boot to the head been torqued, not sure what the torque spec is.

 

If you are able to, swap the wires between the brake and marker light connections. If its miswired and it'susing the brake filamentfor the marker light, you wont see any differwnce in the brightness when applying the brakes.

 

Good chance your rear brake switch is hanging up. Reach down and push the switch is , see if light goes out , you could need to adjust the spring .

 

Thank you all for the ideas. Not good on having to take the carbs off to try and fix, was hoping to avoid that one. The wires shouldn't be switched, they were never taken off and the brake light worked before. Could corrosion cause the issue? It does seem the the rear switch might be stuck. When I hit the rear pedal it seems to stay out but when I push the plunger back in the light still stays on. Could it be a bad switch?
Thank you for your help.

 

If you disconnected the brake light switch and use a jumper wire to connect and disconnect the connections on the harness side you can check if the brake light is working as it should. Clean the connections too. Spray some WD-40 in the socket for the brake light and the switch pin that connects to the spring.

Where did you buy your new inlet boots?

Make sure you have a good connection at the handlebar switch on the right side as the switch casing grounds to the handlebar.

Could the starter spray (overspray) be going into the carburettor/ inlet stub joint where the metal band fits. Mabe the spray is getting drawn in there. Unlikely the new gasket is faulty. Try spraying where the carburettor joins the inlet stub first. Might be a case of slackening the clamps pushing the carburettors forward and retightening the clamps. Worth a try if it saves you removing the carburettors again. It might fix the problem.

 

Is the cover on the inlet boot you connect a vacuum gauge to a tight fit?

 

I got the brake light working, needed a new rear brake switch. Got it from Len at XJ4EVER, he has everything.

Still have an issue with the number one cylinder though. When I start her up numbers two, three and four cylinders get warm after a rew seconds and number one stays cold. After about 30 seconds two three and four start getting hot and one might start to get warm, after about a minute it's hard to touch two, three and four but one is now starting to get warmer. It takes a couple of minutes for number one to get hot. I took the bike in to have it checked out and the carbs synced but the mechanic, who has been working in these bikes since before they came out said he couldn't find anything and the carbs were in synch. He even said for the age of the bike it ran great. Could we be missing something? I took some pictures of the number one and two plugs to see what anyone thinks.

Number one plug.

 

Number two plug.

Thank you for your help.
Joe

 

Thank you.
Joe

 

Number one looks fine number two plug mixture is rich.

 

Thank you for looking Franz. What should I do with number two?
Here's number three plug

 

Here's number four.

 

Three and four look good too. Do you have a colour tune? You can turn the mixture screw on carburettor number 2 clockwise slightly to weaken the mixture.

 

I dont have access to a color tune. Do you think I can just tweak it a hair and go with that? Where is the mixture screw located? Is it between the carb and how would you get to it? Can you see it in this picture?
Thank you

 

I could lend you my gunson color tune. if you're still local.

 

Mixture screws are next to the choke plungers, screws are recessed. Have you got a Haynes manual? The rich one should be turned clockwise until it stops they strip easily and then turned anticlockwise two and a half turns.

 

Mixture screw in front of green dot.