XJ700 Running problem

Hi I have fitted a Stage 3 Dyno in my 700 maxim (Air cooled) and it has a problem in mid range, It ticks over fine and sounds great but at 5000 rpm splutters and runs like a so and so. I have a mac 4 into 2, new stock air filter, clean tank, fuel filter and the carbs are spotless. I have Balanced the carbs, used color tune. I have checked the coils (primary and secondry) Checked cap resistance and also replaced the plugs.

The reason I fitted the Dyno was this fault was there beforehand and assumed it was the carbs becouse the pipes had been changed. I am stuck for ideas.

Is there any tech person out there who can say "I had that problem and it was" becouse if you could it would make my day )

If anyone else can help please do.

I am now sat in front of my computer and am not going to move in case I veceive that vital email ;O))

 

Ive heard of this problem from other people also.

I too have a bit of a sputter or lack of power around the 5K mark.

Im not sure if anyone has been able to figure it out.

For mine Im thinking something with the fuel line. Like its kinked a bit or to tight and restrictive.

 

carbs... you have to do some work dialing them in for the new exhast or change in air filter type and sometimes just getting older.

Both of you ride your bikes at 5000 for a little while - pull the clutch in and kill the engine. First gear in a parking lot would work well.

Pull the plugs and report back. They likely won't be tan.

Cheers,
woot.

 

I today looked hard at the carbs, set float levels, Cleaned the fellows again, balanced them and ran at 5k rpm and I have a white to brown plug, I tried upping the jets from dyno 112 to 116 (no differance, I have adjusted needle height, still the same, I know it is running weak but I just don't seem to be able to get it where i need it.

On tick over it is so nice and it pulls superb when running off mains but as soon as I hit the 5k game over

I also can not get a yellow flame on my carb tune at tick over.

I guess it is somthing I have done but am stuck totally.

Any ideas?

 

Carb tune is a good product for this project... white so you know you are lean at 5000.

http://members.tripod.com/dave_jack/id38.htm

That might give you some ideas... sounds like one part is tuned to compensate for another - meaning it runs right at one spot, but not all the way through.

Can I ask why you went with the stage 3? What came in the kit? How was it running before?

 

It was the same before, I assumed replacing mains, needle etc would cure it, it is a stage 1 and 3 kit in one, the only differance being mains. You are supplied with 112 for stage 3 and 116 for 1,s.

 

Niggling gremlins in the bike suck.

Sounds to me like fuel starvation but you seem to have covered almost everything. The only suggestion I can offer that you haven't mentioned is to check the petcock and vacuum hose between the carb and petcock for blockage. However if you take it for a ride on PRI then that would be bypassed anyway.

Spoke to someone recently who had the exact same problem on a Kwaka. It turned out to be a fractured wire near the ignition module. Had a basic connection but it broke down at higher revs presumably as it was drawing more power. May be worth checking resistance on the wiring.

Cheers
HG

 

When you got the bike did it run properly? or it never did run properly?

I'm not following something - what was changed from stock on the bike to nessesitate different needles?

Also note - I have heard that different brand needles don't flow the same... not sure if that would matter right now.

You need to get more fuel flowing at low speed if you are running lean. Can you check the carb boots - maybe it's not lack of gas but excess oxygen. At higher rpm's maybe the boots leaking wouldn't effect it as much, and at low speed you've tuned the pilots to work with the extra air?

Did you ever try spraying them with something flamable like starting fluid or wd40 when it is running?

 

I now have it bang on, I have set the dyno kit to 116 main jets, set on groove 2 (from bottom) on needles and balanced the carbs out.

I have set the color tune to .25 turn in from rich and I must say it is like a rocket. I have never pulled a wheelie on it through shear grunt. It has a abundance of low end grunt does not flutter at all between pilots and mains and turns into a sports bike at 6.5k rpm.

I took it to the steepest hill I know (living in wales theres plenty) and I could climb between 1k and 3k rpm without any probs right through to top gear )

Next call is to the dyno centre just to tweak it that little more.

THANKS FOR ALL YOUR HELP

 

So what did you do to fix it? what was wrong? Just for future reference when someone else has this problem...

Awesome!

 

I knew it was lean, so I went back to square one. I stripped carbs and blew them through, Reset float hights, checked boots etc. I then went onto start with the dyno set up specs 112 jets for after market pipes 116 for standard. I used the 112 jets knowing the bike was lean but having after market pipe and filter. The recommended setting is 3rd notch from the top.

At this setting I could not get a rich reading so kept going down the needle until one from lowest and bike was pretty good but still weak at top end so I swapped the jets for the 116 and hey presto.


I dont think that there was realy a problem with my levels etc I just think dyno were on about a differant bike

As stated dyno for my bike should be 112 mains and needle set to 3 instead it was 116 and needle set at 5.

I HOPE THIS MAKES SENSE

Oh it is a maxim 700 air with 12000km. I think alot of the trouble was the MAC pipes and dialling them in correctly.

AGAIN THANK YOU FOR YOUR HELP.

 

I wonder how the Mac 4 into 2 pipe compares to the stock 4 into 2 in terms of air flow?

You got it set now - thanks for the notes - good job!