Racing Idle and no power at bottom end

1984 xj750 engine. Carbs??

The bike doesn't seem to want to pick an idle speed.. Sometimes 2k, sometimes 3k, or anywhere in between. And there's a serious lack of power at the bottom end.. Coming onto the motorway I stuck it in 5th and twisted the throttle all the way.. Up to about 6k revs I might as well have been on a 400cc or less, then she started to find power, and at about 8k I had to back off on the throttle because the bike was behaving like you'd expect a 750 to behave..

Would that be the pilot jets all gummed up maybe?

I'm going to put some carb cleaner in the tank and take her out for a long ride, but I was just wondering if there was anything else I should be looking at? I don't want to take the carbs off and clean them at the moment, I've got a colourtune plug to sort out the mixture, and I'l balance the carbs this week, but anything else anyone can think may cause this behaviour?

 

Something's all gummed up, not maybe.

Running carb cleaner through it won't fix it.

You ARE going to have to pull and clean the carbs; otherwise tuning efforts will be frustrating at best.

The passages in the carbs are smaller than tiny; once varnished up they stay clogged until you intervene.

Read: http://xjbikes.com/Forums/viewtopic/t=24010.html

 

Thanks Fitz

i might be new to this foum, but I'm not new to motorbike forums, I was just hoping that the carb cleaner would tide me over for a while until I had time, I desparately need to service my other bikes, as I only have one roadworthy one at the moment, I guess if I'm gentle with the old girl she'll survive, she has done so far.

Really, all I was wondering was if these symptoms pointed to anything other than gummed up carbs.

Also, cleaning carbs, especially the jets; some places use vinigar, some like acetone, some people only use carb cleaner, I even saw one guy in South America (Brazil) who used cola, because it was all he could afford, any preferences anyone, and if so, why.

 

Sure ya don't have an air leak? If ya have a small propane torch laying around, try testing for an air leak. A can of starter fluid will suffice too, but I prefer not to spay stuff all over. The propane leaves no residue and will make the idle go up if sucked in by an air leak.

If no air leak is found, like fitz said, definitely pull the carbs. make sure both idle & main jets are clear. Check for sticky floats. I clean jets with carb cleaner and blow them out with an air hose. If soaking the jets is required, I found that cider vinegar works great. Softens up any crap the carb cleaner cant budge, so they are easily blown out.

As far as putting anything in the tank, Sea foam works damn good, but don't over do it. 1oz of Sea foam per gallon of gas.

Check Petcock screen/in line filter(if you have one)

Good luck man, let us know what ya find.