Need new some help.

My dad has a 82 seca 750. The carbs on it needed rebuilt, so for Christmas I bought a set of carbs for it that suposedly worked well...only problem was I thought he had a 650 so I bought 650 carbs. Anyway he changed the jets from the 750 carbs into the 650 carbs I bought.

The problem we're having is when you start the bike within a few seconds it revs up to 4000rpm and stays there.

Can anyone help me figure out why this is happening? I would really appreciate the help/advice.

Thanks

 

1st make sure the throttle cable or throttle linkage is not hung up a very common problem so double check for the guys,,,good news is you have fuel,,,, you may want to go back to the original carbs so be careful with them,,,your in the right place there's plenty here if you read some older post,,,carb problems are infamous. an by needing rebuilt most of the guys here will think they need a good cleaning,,,something the newer carbs are more than likely going to need also,,,so proceed carefuly,,,,father an son project is a good xmass gift no matter how you proceed,,,good luck hope it's something as simple as the linkage. get this sorted out start on the original carbs as a leaning experience,,,,

 

A carb synch might go a long way for you as well.

 

The MOST Common mistake that we all make after removing and replacing Carbs is to get the Throttle Cable Linkage Connector jammed-in UNDER the Head.

This causes the whole Linkage to remain OPEN and the Bike to run-away with High Revs.

If you have gotten the Cable Pull Linkage Attachment lodged up under the head ... Remove the Carbs to free it and "Tie-it-UP" with a Plastic Tie Wrap or wire.

DON"T try to Pry it loose. You will either break it off and be way up the creek OR Bend the Linkages and have the Rack start getting stuck open on you.

Don't feel bad about having it happen to you. This is a Bona-Fide right of Passage.
You paid your dues.
All you need to do is free it up and your in business!

 

Thanks for the info. I read that in another thread so thought it might be the problem. We disconnected the throttle cable from the carbs and started the bike...same thing happened. It would idle normally for a few seconds then the RPM's jump to 4k and stay there.

Anyway since we took the airbox out and are waiting for the k&n filters, we were starting the bike without the airbox or any sort of filter on the carbs...could this be causing the carbs to be getting too much air in turn causing this problem?

The reason I ask is because if I put my hand in front of the carbs while the bike is running, the RMP's drop.


Edit: on another note...where can I get a new battery?

Also thanks for all the advice so far.

 

I bought my battery at Wal Mart, but you may prefer a higher end product. They are available at most bike dealers and parts stores. Batteries are not as model specific as carb parts. That should be the easy part of your project. Good luck with dad's bike.

 

Yep, that's the problem. A common reason for a high idle is an airleak. With the air box off, that's a big air leak. If you are going to run K&N in the airbox you need to up the main jets one size. If you are running pod filters then you should have kept the airbox. There will be a lot of carb tuning needed to get the bike running acceptable. I don't know any who have tuned out all flat spots with pod filters.

 

for the Batt, I went to Yamahog, price wasnt bad.

 

I found this thread while searching the forum for the same problem. I have an XJ750 that (when it's warm) revs to ~3000 rpm for it's standard idle (at stop lights and such).

I've read about air leaks (vacuum seal leaks), and carb cleaning. I'm not sure I'm ready to tackle a carb cleaning... so I bought the kind you send through your fuel: 'Fuel Injection & Carb Treatment'. I hope this wasn't a bad move.

Anyway... I'm curious how this turns out for you, and if I can learn something about my problem.