Can finally ride my pig.. but missfire at moderate throttle

Hi, I've been working on my project XR650 and now have it all up and running in SM spec.  I've had to release the clutch which was stuck but it's now seems to be nice and smooth after covering it in oil for 5 mins and separating the plates with a knife.

I've gone for a maiden ride and found its riding really well.  Pulls well but as was reported by the previous owner has a slight missfire.   Under moderate thottle at mid revs I'm getting some missing and juddering.  He mentioned it seems to start when the bike hit's 90 degrees on the trailtech.  I've waited for it to hit 90 and sure enough it pulls away fine but misses.  I can still ride the bike.  When letting it cool to around 78 its still mising.

I've put in a new plug, coil, and I believe the stator is also good (new?)  Even some of the electrics have been replaced I believe.  

Can anyone give me any ideas on where to start?  Next time I'll ride it I'll check to see if it's missing whilst getting to operating temp as I was being very gentle.

It must be something simple as these are not highly complex machines right ?

One thing I've not done is change the oil yet. Could overfilling and heat expansion cause a problem?

Sounds like your carb wants a good clean out...did you make an offer on my tank on evilbay ?.....if you did it was too low

"I've had to release the clutch which was stuck" & '2000 model' .....

you're sure the clutch bushing is the new/improved type, fitted standard as from 2003?
Your bike (2000) was shipped with a bush with a smooth inside surface and it must have some machined oilpockets there.
Also, the seal of the sprocket shaft you may want to renew, also to the improved /better version.

Misfire?
It starts right? >> spark's fine if the plug's new, so clean the carb, set it to perfect, and do check the jetting for your altitude.
Have fun!

Mauser wrote:Sounds like your carb wants a good clean out...did you make an offer on my tank on evilly ?.....if you did it was too low

Thanks - I had discounted the carb as when the engine was rebuilt the carb was ultrasonically cleaned. I've taken it off and cleaned it. It was pretty spotless inside though the outside was a bit grimey. My 525 was much worse inside when I did that carb.

I've cleaned the jets with MAF sensor cleaner which I've found was the only solvent which cured my 525 of a misfire after it had been stored for 5 years. I'll post up if it all works.

Yep - that was me on fleabay. It's all I could go to (and all it's worth ) as i only really want it for the decals on the side!

I will check the clutch bushing but I'm not sure what to look for to be honest.

Rawhide wrote:
Yep - that was me on fleabay.  It's all I could go to (and all it's worth  ) as i only really want it for the decals on the side!

Check out
http://www.ebay.co.uk/itm/honda-xr-650-r-fuel-tank-plastic-with-cap-/191962631603?hash=item2cb1dd4db3:g:G-IAAOSwMgdXzLU3

Then tell me how mine is worth £50.....

I was just kidding Mauser. I know just how much parts are for these old bikes. It was a lowball offer but just what I would pay as I only wanted it for the graphics.

I put the carb back on yesterday and took it for a wonderful ride this crisp autumn morning. The missing is still there. It's quite a shudder and making me wonder if its related to the clutch slipping now.
I also have a trailtech vapor on there which I noticed the Amber LED was flashing sometimes when it was playing up. I checked the instructions and this indicates a heat problem. I've put a thermostat in. All this was happening below 90 degrees.
The previous owner though this was heat related and it does seem to be a bit worse nearer to full operating temperature but I can't see a pattern. Any ideas next? New clutch? I've experienced heat related clutch slip before when I clutch lever was touching a guard but the slip causes the engine revs to rise. This is not doing that. It's more like a juddering loss power.
Any ideas welcome guys.

Have you checked the valves ?

Mauser wrote:Have you checked the valves ?

I just set the valves.  The inlets were just a touch tight, one exhaust valve was a little tight and the other set perfectly.  I've set them all to factory spec.  The bike started first kick and is running perfectly.  However just about 200m into my ride the missfire happened again

I'm pretty sure it's now ignition related.  The plug looks fine, (as it's new), the lead is also new, coil is new..  after this I'm thinking things will get trickier to replace, especially as the CDI (also new I'm told) has had the connections glued in

Any ideas from this point welcome.  I'll do an oil change tomorow but I'd doubt an overfull bike would cause a missfire. It does seem to be happening at higher loads, gentle throttle it's fine, higher revs and making the engine labour more seems to make it struggle more. The loom does look a bit of a mess. I'm wondering if I should start disconnecting things such as the headlight. The trailtech indicates around 20v when it's running.

If your local to me I can lend you a CDI to try out....spin around the block and confirm if that's the problem ?...these bikes are simple in design and electrics...have you checked all grounds are good ?

Mauser wrote:If your local to me I can lend you a CDI to try out....spin around the block and confirm if that's the problem ?...these bikes are simple in design and electrics...have you checked all grounds are good ?

Thanks for the offer Mauser. I'm not that local and annoyingly the previous owner has glued in the connectors to the CDI unit as the plug must have been cut off the loom. I'm thinking that must have been done as the CDI was considered 'good' so I'm thinking it's more likely to be the loom than the CDI unit.

I'm going to check over the loom properly first before I look at the CDI unit.

I would replace the loom specially if it's been cut ?, if your going to keep the bike it's well worth the little cost to replace it...
http://www.cmsnl.com/products/harness-wire_32100mbn640/

Or try ebay ?

I stripped back the loom from the headstock back to the CDI unit. It all looks intact. There are some connections with blue insulation tape which I couldn't tell if were designed that way from the factory. They seem to splice the wire into either a pair or more wires. I've seen similar on a car loom so I'm assuming it was factory. Either way I've tidied it all up and put new tape on.

In moving around the wiring I noticed one connection to the CDI had come away. As the CDI has no plug and only wires glued to the terminals I had to solder the black/red wire to its connector. Not ideal but it's probably a better connection than was on there. I've started the bike so know it starts again but I'm banned from warming the bike up whilst the kids are asleep so will need to wait to see if I've made a difference. I doubt I have unless it's the dodgy connection to the CDI unit.

I do have a few questions;

1) Mauser, you mention checking all grounds. I can't see where the grounds are except for the coil. That ground is definitely good as I had a mechanic check out that area as I had to reverse the coil mounting as for some reason the lug which it screws into has broken off. Quite how that could happen is baffling me!

2) Does anyone have a wiring diagram where the colours can be read? I've tried the manual and some links I've found but the scans are too low quality.

3) The trailtech says at idle the bike is making around 17volts of power. With some revs this is around 20volts. Is this a normal output? I stopped short of removing the stator or counting wires to see if the stator is standard.

Sorry for dumb questions, I'm learning a lot here.

Here's my wiring the loom should be similar apart from you will have the extra's for lights. horn, indicators etc....mines slightly odd as I added a horn circuit but currently run the bone stock US loom....they do splice the wires as you mention...that's normal.



Your stator should produce AC which feeds the CDI and also the regulator and from the there it's rectified to DC  to run the bikes electrics headlight and horn....

Thanks for that diagram Mauser. I took the bike for a ride again earlier and I really was sure I'd fixed it as it was driving so well as it was getting up to temp. However as the bike got warmer it started to run rougher. I did notice as I pulled over to let the engine heat up it jumped instantly from 70degress to 90degrees instantly, then back to 70 again. This can't be right.

I've put a new thermostat in the bike already. It was running without one when I got it.

I recorded a short video as well.



My next step will be to give the carb to a bike shop who will clean it for me. I'm not sure this will cure it but It's one less cheap variable to worry about.

Whilst the loom has been messed about with I can't see how that would affect the AC power going to the coil. I'm also thinking CDI failure would mean no running, rather than rough running.

Any ideas really welcome. I don't want to replace the loom unless I really am sure it's that.

Yo Raw,

those 'factory' splices, taped blue - how's the electrical connection done?
Wound-around, cold-pressed (crimped), soldered?
If not soldered I'd solder them, with a LITTLE solder - no big loooong blobs etc, just a dab to ensure proper electrical connection (and use fluxcore solder, flux is your friend here).
Wound'around wires have a habit of intermittent contact on a vibrator (don't ask how I know this please? ), and when the pig has been swimming in his past corrosion will be present too.... solder them all, also when they're crimped.
Taping them up again is also crucial (after soldering them) so that the splice is supported by the tape.... soldered wirtes do not bend anymore you see, hence my advice for a small solderspot only (NOT al long one!)
Then lastly, get a new NGK plug, take any doubt away!
Oh, the ground-tab between frame and HT-coil you better remove, clean all surfaces, then remount with a thin coppaslip-smear inbetween all surfaces.... this will last you a lifetime and ensures a good connection.
Good luck!

More, just saw the vid (nice bike so btw!)

Got a 68S idle jet?
GET it if not, and I bet you don't
(If you have a TM40 carb better enrich your idle jetting, this is in fact what the S-bit does)

Also, this bike overheats quickly, the cooling is marginal at best: it's perfect when one keeps going, like racing in a desert, but idling and traffic lights etc is NOT what this bike is for, neither struggling in technical sections when the going gets tough.
This bike will run all day at 110 degrees Celcius and will be fine then (convert yourself, that's a LOT more than what your temps are). But, get the 1.6Bar rad-cap, the 1.1Bar is too little (and is the std OEM cap).
Stop when it boils, let it cool down - and if this happens often you either need a fan or dual-core radiators.

BuRP wrote:Yo Raw,

those 'factory' splices, taped blue - how's the electrical connection done?
Wound-around, cold-pressed (crimped), soldered?
If not soldered I'd solder them, with a LITTLE solder - no big loooong blobs etc, just a dab to ensure proper electrical connection (and use fluxcore solder, flux is your friend here).
Wound'around

This is an example of the joins. I'm probably going to do a worse job separating them than Honda did with their copper sleeves.

The coil as I mentioned is mounted in reverse as the front lug of the coil mount on the frame is broken. I did have a bike mechanic check out that setup as I was concerned that might affect the earth. He also made sure the ground was good but next time I'm in there I'll check to be sure the frame is clear of paint etc but I'm pretty sure it was and the mechanic was fine with it. However it must be something simple so I will check everything.

The plug is new already as well. I am doing much first enduro this weekend so won't have time to work on it this week as I'm prepping a wr250f. Carb will be done next.

Here is the mess of the CDI unit along with the wire I soldered up to the terminal. However it did not solve my problem



I appreciate the replies.