Rpm redlines when starting

My 82 XJ750 Maxim would barely start and run as if the carbs neded cleaning. I took them off and cleaned them. I have cleaned the carbs on this model bike many times. I put around 100k miles on my previous one.
Since I cleaned the carbs, when it starts it redlines and I do turn it off immediately. I have removed, inspected the carbs a few times and still get the same result. I suspect the cold start circuit and have inspected it, but can not figure out what's casuing this. What could cause this besides the cold start circuit?
My bike is my only transportation and I have to get it running.
I also get the same result without the throttle and cold start cables attached to the carbs.

 

Sounds like one or more of the butterflys is catching, loosen the 2 screws & force the butterfy in with your thumb & re-tighten the screws.
It doesn't take much to get enough air to lift the pistons & off she goes.

 

It could also be a vacuuum leak (possible at the throttle shaft seals). If adjusting the throttle plates does not help then check for vacuum leaks using a spray can of carb cleaner.

 

first time cleaning this carb set? was it a complete disassembelly?
did you replace any parts ?

 

I had to clean and replace a couple of jets and other parts for the catbs to get it running after I got it a few years ago. It ran great until recently. All I have done this time is clean the jets, passages etc. I have never seperated the carbs.

This could be a vacuum leak? I thought you check for that by spraying the places that might be leaking and if the rpms increased it means there is a leak. It redlines as soon as it starts now.
I am checking to make sure the butterflys close. I think they may gotten out of sync somehow.
Normally if I have a carb problem its the opposite and doesn't start or barely runs. This problem has caught me of guard.

 

If it redlines as soon as it starts then it's either a mechanical issue (binding throttle plates, binding slides, or a binding cable, or a vacuum leak. You are correct about how to test for a vacuum leak, but the symptoms of one are a racing or hanging idle.

 

so the carbs worked before, and you did a reclean did not take carb apart other than to access the jets, then look the work you did.
linkage binding? carbs back in boots properly, boots clamped. could be boots have leaks or gasket failed boot screws tight? air jets reversed?
check tour Idle adjustment knob position back it out, check for proper slack in throttle cable vac caps installed vac line hooked up?
can not see it being your butterflies if you did no dissambly

 

Thanks for all the help so far.
I misunderstood vacuum leaks so that is my prime suspect now. I have checked everything else mentioned above.
Can't believe I ridden an XJ so long and had very few problems over all. I need to ride to keep my sanity.

 

if you had your mixture screws out did you put them back in in the correct order spring on screw followed by washer then oring last?

 

I never could find a vacuum leak but I got it to start without red lining. I noticed a pilot air jet was blocked and I cleaned it. It started up and seemed to run good at first, but after it ran for a few minutes it started running rough. Looking at the spark plugs, it is running rich on 3 cylinders but one plug looks good. The carbs looked good when I had them apart and checked everything.

Looking at the adjustment screws, the air fuel mixture were adjusted when the PO had the carbs cleaned and let it sit for a year and so I had to rebuild them and replaced some jets etc that needed it with parts from chacal. I bought it from he original owner who purchased it new and it still had the original tag. He had the exhaust replaced with a 4 into one and the center stand was removed. I prefer the sound of the original exhaust and really miss the center stand.

I think I may need to work on adjusting the fuel air mixture now.

 

check the mixture screws foe vacuum leaks as well ,
color tunes work well for adjusting mixture screws start at 2-1/2 turns on most bikes
center stands are a must have makes life so much easier.

 

Vacuum leak

Or another possibility-- check to make sure you have the AIR jets in the right places. Some of them are able to fit in the wrong holes and easy to mix up and reverse the positions

 

I am going to take off the carbs and give them another good cleaning and check everything else before I adjust the fuel air mixture. Knowing that has obviously been adjusted before, makes me think it could be a problem. Eventually I want to rea e the petcock with a simple on and off one. I don't mind having to remember to turn the gas off. Also will get a valve cover gasket from chacal when I can.
Iam missing the road and wind more every day. I even miss riding in the rain or freezing temps, just never both at the same time. Just got an almost new nice kbc helmet I need to try out too.

 

You said 3 cylinders are running rich, you may want to check the "O" rings in those carbs they may be deteriorating I had the same problem occur rapidly while driving when it started to flood. here is a pic of the parts you will see one still has its o ring, this caused major flooding after and set my bike on fire due to a backfire.

 

I think these are the jets not sure, new to bikes. I replaced the rings and it ran fine after.

 

The 750 does not have that type of fuel valve in it. Those are for a 550, and other Mikuni carbs

 

Good to know, thanks Hogfiddles, I will have to open up mine and see sometime this summer, I have an xj750 to rebuild later on too....lol

 

it this thread for xj 650 there is a photo posted by K-moe showing correct location
thread is about typo in haynes manual
http://www.xjbikes.com/forums/threads/typo.85507/#post-504993

 

Those are the float needle seats (you can see the tops of the needles sticking out of the top of each seat). The 750 has a fiber washer that seals the seats, instead of an o-ring. They can leak there, but it is less common.

 

Got her running better but now I need to get insurance, title and registration. I need to ride so I can tune the carbs more. The carbs have been off and gone through about 5 times so now I am working on the air fuel adjuments and have made progress. Don't have a color tune plug yet. Just need her running decent now. Will get a valve cover gasket ane color tune plug when I can. Then adjust the valves and get the carbs tuned in better after that.