1985 xj700 cutting out in mid rpm

Just bought this 1985 xj700 Bobber for 1300 runs good but cutts out between 5.5 and 7,000 rpms on the free way help please!

 

Adjust valves
Remove carbs
Clean & rebuild carbs
Wet set floats and bench sync carbs
Reinstall carbs
Color tune
Remove rear wheel, replace brake shoes
Replace rubber front brake lines

Check back with us after this is done.

 

Carbs are brand new I have the recite but I'm not all that mechanicly enclined. Do the jets need to be tuned ? Also it's running straight pipes might that be an issue?

 

Brand new carbs, as in never been used? That opens up a whole series of questions;
A. Are they the correct carbs? Lots of different carbs could be made to fit your bike, or any inline-4 engine for that matter, they could have been cheap and looked right enough. Never assume the previous owner really cared enough to do things right. You are in possession of something of his which most likely was created out of a sense of fashion and not mechanical efficiency.

B. If they are the right size, is it jetted properly? This is a huge issue, especially since I gather your bike is running pods along with the straight pipes. But even just changing the exhaust would necessitate changing jets.

C. Are the carbs actually clean? Did the bike sit for a significant length of time, anytime since the "new" carbs were installed? They could be just clean enough to run, but not run right.

As others will surely jump in and tell you, you need to make certain, as in do it yourself, that the valves are in spec. Then sync the carbs.

 

XJ700 Chopper
Thats your problem right there

 

How is that a helpful comment?


Hadden_13, Have a look at the carbs that you have. There should be ID markings cast into the carb bodies. Lets start by fully understanding what it is that you have. Pics of the bike would be helpful, particularly of the engine area, so we can check for any other modifications that may be contributing to the trouble.

 

I will post more pics in a few moments

 

Having a hard time posting pics. K Moe do you have an email I can send them to ?
The carbs are mikuni Corp same as my four wheeler and dirt bike guessing it's a Yamaha thing !

 

You have to use a photo hosting site and link the pics.
Do the carbs have individual filters, or the factory airbox?

 

They have one filter that runs across all 4 it's a red foam filter

 

OK.

Let's back up here. Is it an XJ700, or is it an XJ700X? The straight 700 is an aircooled motor and should have Hitachi carbs.

The "X" motor is watercooled (so there would be a radiator) and came equipped with Mikuni carbs.

The air filter you're describing plus straight pipes means that jetting work would have needed to be done to the carbs; and whoever did it probably didn't get it right.

Further, it is highly doubtful that you have "brand new carbs." Freshly-rebuilt, maybe. Lots of new parts installed, sure. However, if whoever rebuilt them didn't do certain things right you're going to have difficulties.

However, there's a deeper issue at hand: "I'm not all that mechanicly enclined."

That's going to have to change. A 1985 Yamaha in stock form is a DIY proposition to begin with, as most shops simply won't touch bikes this old or don't know what they're doing. A heavily-modified bike such as you have is going to require a lot more mechanical attention than a stocker and you're going to have to do it.

 

It is liquid cooled and has mikuni carbs is the x middle something special?

 

So to confirm you have an XJ700X, which is a water cooled bike. Stock it looked something like this

Notice in front of the engine, above the exhaust pipes is the radiator. If this looks like your engine, you have an "X". Without the radiator, you have an air cooled XJ700. The "X" has a lot more power, but otherwise is not tremendously more special than the air cooled version.

 

I have a radiator ! And it is very powerful I used to own an old ninja and this thing would eat it for lunch, engine looks similar bike looks nothing alike lol

 

Ok just making sure, some people mistake an oil cooler for a radiator.
Still waiting for pictures, btw...

 

The "X" motor is the same watercooled, 5-valves per cylinder motor that Yamaha used in the FZR series; essentially a sportbike motor in a cruiser chassis.

So yes, it should have Mikunis.

The reason this is important is that a lot of the "answers" provided will be different for an "X" than for an "airhead" (aircooled) XJ. There are quite a few differences between your bike and the aircooled bikes.

Honestly, the easiest way to get that bike running properly would be to return the intake and exhust systems to their stock configurations. It was an absolute screamer in stock form; believe it or not it was even FASTER before the mods.

 

Especially since it currently doesn't run correctly :lol: