Starting issues

Hello everyone, I am new to this site and new to XJ's. Having just got Maxim xj700 1985 today. I was given this as a non runner. The previous owner said that it was running fine (ish) then one morning it just would not start. I have been playing with it a bit and can now get it started, with full choke, it idles nicely but as soon as i increase revs it dies instantly. Sometimes it will rev up but starts to backfire badly. Also as soon as I take the choke off it dies. Anyone have any ideas what I should check first.

Thanks in advance.

 

Sounds possibly like a vacuum leak. You could pass an unlit propane torch around the intake area while it idles and see if the speed increases. If it does, you have a leak. The carbs probably need cleaning and setting anyway if its sat for any period of time. The stale gas turns to a varnish and plugs all the orifices and generally gums it up.

 

cool, will try that, don't have a propane torch, will quick start or wd40 do the same?

 

Starting fluid should work for this. I wouldn't try the WD-40... too messy.

 

Ok so sprayed some quick start on the intakes, second carb rev'd up hugely. So guess I have a leak there. Took the air filter out and sprayed carb cleaner inside. It is now running and revving. But, in neutral it is revving up to about 4000 rpm and sticking there. In gear it is fine and behaving itself, is this to do with the leak?

Can I Repair the leak? do I need to buy a new rubber? Can I replace the whole air box system with K+N cone filters? if so, do I need to re-jet? Sorry for all the questions. Just quite excited by the fact that I have been given a bike, which appears to have very little wrong with it.

 

Could be the intakes (carb mounting rubbers) or throttle shaft seals, or a vacuum line. Check the Intake rubbers for cracks visually. You can try to pinpoint the spray at the throttle shafts and other suspect spots. If the carbs haven't been rebuilt recently, after sitting for extended period, its probably time. The high revving could be caused by sticking slides. You will hear (read) a lot about "clunk test".. If you need to get into the carbs, don't take shortcuts. Do it right, do it once.

 

Thanks guys, cleaned the carbs and sync'd them. Still sticks a fraction on return but not too bad. Gonna get them ultrasonically cleaned. Passed MOT today, couple of advisories but nothing too bad, forks and front tire. Anyway, time to strip it down and bob it me thinks, so you may see me on this forum quite a bit from now on.


FREE BIKE!!!!!! WOOHOO!!

 

admiral.snelson Hello and welcome to the forum. There are a number of members on here from the London area. I have to get my 83 XJ750 certified soon, I'm in Ontario also. What all needs to be up to par? And what are the issues with the forks and rear tire? Just don't want any surprises when I take her in.
Oh yes I had the same issues you are having and it was ALL about the carb needing to be cleaned properly, no short cuts or you will just have to start from scratch. Then bench synced, vacuum synced, color tuned and tweaked, then fine tuned plug chop small adjustments to get pug color right. And so on. You will find ALL the information you need to make her run like a top on this forum. Just listen to the likes of Bigfitz52, RickCoMatic, Robert, and many other wise old XJ'ers.

 

Sorry mate, London England. Not sure what the regulations are in the states. Over here they gave me an advisory that the front tire is worn and there is a smattering of oil in the front forks.

 

Boy do I fell dumb