650 cutting out above 4,000 rpm?

I'm still working on the NX650 (same engine as an XR650L)I picked up a few weeks ago. Things are shaping up but I have an unusual problem I can't quite figure out. The bike starts great. I allow it to idle and warm up for a couple of minutes ands it idle smooth. After that if I try to rev it up past 4,000 it starts cutting out and the tach jumps all over the place. I've replaced the plug, adjusted the valves, rep[laced the air cleaner and installed a new battery. What am I missing?

Thanks for your help!

SteveON

if you have one, try another cdi box.

Unfortunately I don't have a spare CDI box. Was kind of hoping it was something different but not sure where to start looking?

the only thing controlling RPM limit is the cdi and this definately sounds electrical. i would first make a check of all ground points. then maybe check ALL electrical contacts/connectors.

i dont think this is a stator issue.

So many parts are interchangable on the XR range.You may even find that an XR250 CDI will work..mid 80's model..Always pays to have spare stuff lying around.I ran one on my 86 XR600.Theirs basically no difference in those engines through to 93(baring maybe cylinders)..even ran it on my 85 XL600..Worked perfectly and a straight plug in job.

good point horri.

there is a guy in vintage forums "streetscene" i think is his UN.

he has a program that cross references part numbers to see what bikes a single part was used on. look him up.

Certainly be damn handy to know that info.I spend countless hours studying part numbers over at the Honda online parts dept but I still can't figure out what can be changed around with what..Subtle part number changes lead to confusion.

Certainly be damn handy to know that info.I spend countless hours studying part numbers over at the Honda online parts dept but I still can't figure out what can be changed around with what..Subtle part number changes lead to confusion.

i sent him a message, so we'll see what he says.

I'd really like to know as well. I'm feeling the CDI box is the culprit. I'm searching online for a replacement but nothing has come up yet. I was also looking for a CDI for a XR650L, I had read somewhere they were the same as the NX650's. But also read the XR650R were different because of the starter vs kick system?

A little technical for me to grasp. I just need a new part. BTW..where is the CDI on the bike? I've found the coil, the rectifier but have no idea where the CDI box is hidden?

Dont rule out the coil, i have seen them work well at idle but when under stress they cant produce the voltage to ignite the mixture.

I was going to suggest checking the coil as well. In my case, jetting changes did nothing to get rid of a midrange stumble. That ruled out the fuel, so the first thing I happened to check was the coil. The connectors were so loose they would rattle and break the connection intermittently. I squeezed them down and the stumble went away completely.

I've been thinking about this all evening. I didn't have this problem until I removed the rear fender and turn signals. At least I don't recall it before. I'm wondering if perhaps a the ground wire isn't tight? Tomorrow I'll be in the garage all day trying to figure it out. I'll check out all the connections, coil, plug wire, etc. Just in case does anyone have a good source for a CDI? Ebay only has them for XR600R, haven't found anything for a XR650L or NX650 (even better)?

BTW thanks to everyone who has offered suggestions.

SteveON

ron ayers has cross reference http://www.ronayers.com/ use the where does this fit bar you can copy and paste the part number

I've been thinking about this all evening. I didn't have this problem until I removed the rear fender and turn signals. At least I don't recall it before. I'm wondering if perhaps a the ground wire isn't tight? Tomorrow I'll be in the garage all day trying to figure it out. I'll check out all the connections, coil, plug wire, etc. Just in case does anyone have a good source for a CDI? Ebay only has them for XR600R, haven't found anything for a XR650L or NX650 (even better)?

BTW thanks to everyone who has offered suggestions.

SteveON

unfortunately the 600r cdi wont work(im sure you know). unless you can rig up an inverter that will handle about 400 Hz or so.

if this happened right after pulling the fender, then look at all your conections related to the area.

I found a CDI box from RMSTATOR out of Canada for a XL600 / XL600V TRANSALP. The XL600 was a single and was made from 83-88 from what I've read. I was wondering if that CDI would work on mine?

thats an AC system. the xrl is DC.

martinfan30 .. thanks for letting me know about that CDI.

I found the problem. The bolt on the bottom of the coil was loose. It has two ground wires connected to it. I cleaned everything up with carb cleaner and replaced the bolt and now it runs perfect! I also finally found a new CDI from BikeBandit. They ordered it for me ($126), I should receive it by next Wed if they can get it. BikeBandit's part number for the item is under OEM>Honda> BikeBandit part number 172156-001. Just thought I'd post that in case someone else has the same problem later! I figured it doesn't hurt to have a spare!

Thanks to everyone who replied. The project is getting closer to being finished all the time. Hopefully I'll finish the painting and it'll be on the road before Christmas.

SteveON

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