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600r cutting out at higher RPM

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So as the title says my bike, once warm, does not like more than 1/4 throttle. Here is what happens. I warm the bike up. Travel at low speeds in my neighborhood for about .5 miles, then get on the highway. I can wind 2nd out just fine but once I get into 3rd and roll on half throttle it starts to cut out. no power. It's like if I just put my finger over the kill switch. RPMs come back down and it runs perfect. Doesn't stall just purrs.

It starts first kick Idles great and will maintain idle speed. Throttle response is great. Here is what I have done so far and some bike info.

1992 XR600R. Stock carb. Header, stock pipe with the silencer removed, snorkel taken out, and a UNI filter

Cleaned the carb.

Main Jets tried every one between 155-170 currently 168

Cleaned the petcock.

Float adjusted

Plug is tan and fairly new

It must be something eletrical. CDI maybe? My ground on the coil is nice and clean. None of my wires are worn out or through. I do have a 55W bulb in the headlight, but the bike seems to run it fine at low RPM.... That couldn't be a problem could it? I would hop on it now to eliminate that idea but its dark.

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Don't think I'd be worried about the headlight unless it was shorting

out somewhere,,If that was happening the bulb would probably just blow.

It could be the CDI it could also be the ignition coil breaking down under  

a bit of load. Do you have any spares or a mate with another XR250/350/500/600.

I'm loathe to tell people to buy new bits when they may not be the problem.

A CDI from any of those bikes will work in yours as will the ignition coil.

So,,any mates with one of them or not??,,If not you're going to have to spend

money obtaining one or the other or both for the test.. Then again they may not

be the issue,,see the dilemma..,Be preferable you get the CDI from another RFVC motor

though not vital. Some of the other earlier models ones work as well..coil,,same.

Edited by Horri

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You could try checking the spark before and after warming up the bike.

It does sound like weak spark causing your problem.

As Horri said...start with CDI and coil after checking the obvious things like poor connections.

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Make sure all electrical connections related to the ignition are secure, check resistance of the pulse generator and stator, and make sure the fuel tank is venting properly.

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<p>I'll just add that should the Tank venting thing not work and you're in

the market for a new aftermarket CDI these look like a bargain. I'm tempted

to buy one myself for the 600s as a spare as I'm about 90% certain they will

also work in the RFVC 500/600 and XL600.,Only thing putting me off at present

is the $35.00 shipping cost to NZ..One cent more than the actual cost of the item.,May yet go for one.

,,Comments even state they work in an XL600 and GB500. That means they certainly work in the XR600.

  http://www.ebay.com/...ssories&vxp=mtr

Edited by Horri

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After it warms up & gives you the problem in 3rd gear , try setting choke to 1/2 . & try your test run again. If problem seems to disappear, or minimize, you have a fuel leanness problem. If the symptoms are same, I would focus on electrical , like you have been doing.

Edited by bork

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Thanks for the tips guys. I went through the harness again looking for worn wires, and loose conections. I checked the resistance on the pulse gen, coil and the harness between the CDI and the plug, everything seemed to check out alright. Made sure the tank was venting properly and ensured that there was ample flow through the bowl.

Looks like I'm going to order a CDI. Thanks for the link Horri, I found one from the same company for the 600, I will probably order from them. By chance a xr100r CDI wouldn't work would it? I've got one of those handy parked right next to the big bike.

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I wouldn't know whether an XR100 one would work. Doubt anyone's ever

tried it. If the plugs sort of matched and you were a Desperado Dan

I suppose you could have a look at it but really at $35.00 for one of

those new ones that fit the 600 you can't go wrong. Remember, I only said

the CDI may be the problem, There are no certainties with these things.

The ignition coil from the 100 may be worth a go to eliminate that

as being possibly faulty on your bike..Wouldn't be sure a 100 one would do the job but you never know

your luck.

Edited by Horri

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This is a long shot, but has helped in the past and was an old racer trick in the day to increase spark. Pull the plug cap off, unscreww the copper fitting at the end of the cap (it has a fitting for a flat head), remove it, the spring and the resistor. Replace the resistor with a small piece of 6 gauge copper wire and put it all back together. Then check the spark. If its the CDI, then there will be no change in the spark.

For everyone else, this will boost spark and maximize combustion. In colder times of the year you can also increase gap and it will help with starting.

I am sure this has been mentioned 100 times on hereand this will apply to all resistor type plug caps.

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Don't waist your time modifying the plug cap...the resistor is there to help the ignition and not just for interference suppression.

Just check it (something like 5K) and start looking for the real problem

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Don't waist your time modifying the plug cap...the resistor is there to help the ignition and not just for interference suppression.

Just check it (something like 5K) and start looking for the real problem

Roger. The plug cap mod wasnt meant to be a replacement for anything, its a diagnostic tool for the CDI. Not that the resistor is going bad or needs to be out of there, but it is an item along the chain that affects spark. Kind of like when you have a bad electric stove. You dont just run out and buy a new stove, but first start at the breaker, then work the connections at any junction boxes, then any fuses along the way, so on and so on. Its a guessing game and unless you just want to drop the cash to replace everything, you just start at one end and work your way towards the other.

So, dont waste your time on diagnostics. Drop the cash and fix everything. Heck, you dont even need any advice off the forum because we all make so much money we should sell the XRs and get a new CRF.

Okay. My panties are nonlonger twisted. Come on Rog...lets go ride. Afterwards, first beer is on me.

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No, you were right. The resistor isnt going to tell you crap except you have a bad resistor.

Let's hug, man!!!!

But honestly, you were talking about the fuel drain prior to start up to clear moisture. Since moving to the east coast i have noticed a lot of moisture in the exhaust on start up. What a pain in the arse, but is that pretty common? I'll do a quick clear and bright test if it saves havingnto kick it 10 times in the mornings.

Yikes. Thread hi-jack alert.

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Water is a product of combustion..you are only seeing it coz it's condensing on the cold pipe. :smirk:

Well, draining the bowl didn't work anyway. It appears to be pretty picky regarding the idle on start up. But, I think we are good to go.

So, any word on getting the bike fixed regarding cut out at higher RPM. (I figured we better bring this back to the original topic)

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Water is a product of combustion..you are only seeing it coz it's condensing on the cold pipe. :smirk:

Yup x2

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By chance a xr100r CDI wouldn't work would it? I've got one of those handy parked right next to the big bike.

It's not very likely, although I suppose you could try one if it has the same connections. It's also not likely to have anywhere near the right ignition curve.

But honestly, you were talking about the fuel drain prior to start up to clear moisture. Since moving to the east coast i have noticed a lot of moisture in the exhaust on start up. What a pain in the arse, but is that pretty common?

How much visible moisture comes out of the exhaust is also significantly affected by atmospheric conditions. Elevated humidity pushes the dewpoint to a higher temperature, so more of the exhaust H2O condenses into steam droplets before dispersing. It's usually too dry here to see exhaust condensation, but occasionally, especially after a winter rain, my vehicles billow steam at startup.

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Well, draining the bowl didn't work anyway. It appears to be pretty picky regarding the idle on start up. But, I think we are good to go.

So, any word on getting the bike fixed regarding cut out at higher RPM. (I figured we better bring this back to the original topic)

Try running it without the air filter side cover on and see what happens. My XRL did something similar except not as extreme as yours. At full throttle she would run fine till in the upper rpm's in the upper gears, then it would shut off, once the rpm's came down she would run fine, it was the DynoJet #165 main jet the PO installed, I put in the dj #160 and it went away. Also make sure the retainer that holds the needle in the throttle slide didn't come loose, with the XRL it can cause all kinds of strange problems. Good Luck

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Try running it without the air filter side cover on and see what happens. My XRL did something similar except not as extreme as yours. At full throttle she would run fine till in the upper rpm's in the upper gears, then it would shut off, once the rpm's came down she would run fine, it was the DynoJet #165 main jet the PO installed, I put in the dj #160 and it went away. Also make sure the retainer that holds the needle in the throttle slide didn't come loose, with the XRL it can cause all kinds of strange problems. Good Luck

yup, this would simulate a leaner condition without air filter. Which if runs better without filter, means you are jetted too rich.(too much fuel over air)

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yup, this would simulate a leaner condition without air filter. Which if runs better without filter, means you are jetted too rich.(too much fuel over air)

you don't take out the filter, you just remove the side cover to the air box.

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