another standard carb issue

Zoro wrote:What about valve adjustment, where is that at the moment?
You'd be surprised how much better/ smoother these things run with the valves adjusted correctly.

Be sure to disconnect the decomp cable from the lever prior to adjusting them and triple check the gaps by turning the engine 720 between checks.

Hi Zoro i just set the valves to the standard specs and checked them last week so the valves should be good.
altho i did not disconnect the decomp cable, i didnt think that would be necessary for checking/adjusting the valves?

i know its a long shot but would there be any way to tell if the crank has been changed to a stage1/2? as i know the valve specs would be different if that had been done by a previous owner

A good indication of cam change would be the lack of decompressor. You might still have the lever but does it actually work?
Mine runs great on the settings I gave you, runs fine with the larger MJ's too. I wonder if the ACV bladder is leaking air as in it has a hole in it? The mod doesn't account for that, you're probably better off just blocking the vacuum port and eliminating a leak path. One other thing I do to mine is fill the gap around the mixture screw with grease to prevent a possible vacuum leak.
Does sound electrical though, you're not on the limiter are you??lol
Let's assume the carb is fine, its breaking down at rpm. Coil/ ht lead or plug/plug cap?
Could be something stupid like your kill switch playing havoc at high rpm/ vibes or wiring harness issues?
A connector not fully seated or dry contacts etc..
Swap plugs/ correct rating??

Just thinking out loud here and throwing ideas into the wind.

I would at least put the 68S back in, it should run fine on any mj between 170-180 for this exercise. At least put it back to your best combo.

There's other issues at play here me thinks...

Zoro wrote:A good indication of cam change would be the lack of decompressor. You might still have the lever but does it actually work?
Mine runs great on the settings I gave you, runs fine with the larger MJ's too. I wonder if the ACV bladder is leaking air as in it has a hole in it? The mod doesn't account for that, you're probably better off just blocking the vacuum port and eliminating a leak path. One other thing I do to mine is fill the gap around the mixture screw with grease to prevent a possible vacuum leak.
Does sound electrical though, you're not on the limiter are you??lol
Let's assume the carb is fine, its breaking down at rpm. Coil/ ht lead or plug/plug cap?
Could be something stupid like your kill switch playing havoc at high rpm/ vibes or wiring harness issues?
A connector not fully seated or dry contacts etc..
Swap plugs/ correct rating??

Just thinking out loud here and throwing ideas into the wind.

I would at least put the 68S back in, it should run fine on any mj between 170-180 for this exercise. At least put it back to your best combo.

There's other issues at play here me thinks...

thanks for the information Zoro, i do still have the decompression lever and yes it still works so would it be a safe bet to say the crank is the standard one?

also does the decomp have to be disabled to do the valves on these?

i have used the bike for maybe 10-15 miles today an i can safely say its not on the limiter, even if i pull out of a junction and just pin the throttle it loses all power until i roll off the throttle.

i will try and pick up some fuel resistant silicon to seal the vacuum hole but i did give the ACV a good inspection and it looked new, it was a tight snug fit with no holes.

did you fill it all the way to the seal around the mixture screw with grease or just a thin layer?


I am starting to think its not the carb after all this since the constant loss of power on full throttle has calmed down now and then but never gone away like others have had happen after a carb service but i wouldn't know were to begin with the electrics haha

It will be for the best to install my carburettor in your bike to see how it runs then , if it still runs bad we can rule the carburettor out , this is the only way , you lucky that i only live few miles away

Mad Frosty wrote:It will be for the best to install my carburettor in your bike to see how it runs then , if it still runs bad we can rule the carburettor out , this is the only way , you lucky that i only live few miles away

i think you might be right frosty.

Cheer up man , we will sort it

Mad Frosty wrote:Cheer up man , we will sort it

oh i hope so frosty, my other bikes now off the road for a few month since i have been sinking all my spare cash into this.

At least it looks like i will have lots of carb spares

Kirky, take Frosty's carb and give it a go, let us know.

Zoro wrote:Kirky, take Frosty's carb and give it a go, let us know.

This is going to be the most intensely watched carby swap on planet earth, may the force be with you

I also like to intensely watch Beavers too, but that's a whole nuther forum...

beaver350 wrote:

Zoro wrote:Kirky, take Frosty's carb and give it a go, let us know.

This is going to be the most intensely watched carby swap on planet earth, may the force be with you

HA i just hope it works so i know what the problem is and as for the beavers it depends what type of beavers you like to watch

I have a day off tomorow , need to get to Darlington in the morning , should be back just before 12 oo , if you wanna come here and so we can fix the bike , i will be working on saturday

Double post , it must be the beaver effect

Mad Frosty wrote:I have a day off tomorow  , need to get to Darlington in the morning , should be back just before 12 oo , if you wanna come here and so we can fix the bike , i will be working on saturday

hey frosty that sounds great, i will fetch all the spares i have as well and tools

What's wrong with my tools

Mad Frosty wrote:What's wrong with my tools

Not greasy enough

Mad Frosty wrote:What's wrong with my tool

Well Frosty, you seem to be into beavers?
Ask them!

The beavers have told me last night that there is no way the whole tool will fit in , so yes apparently i need a smaller one

HUGE thank you to frosty for his help today, it looks like its my arch enemy and that horrible witch craft known as electricity to blame for my running woes

we tried a few idea's with the carbs, swapped mine for his but still no luck until we swapped the cdi and hey presto....
now i just need to find a replacement cdi

oh and swapping from your cdi back to mine for the trip home seems to of affected my vector speedo slightly, its gone from Fahrenheit to Celsius, mph to kph and it said i was doing 385kph on the way home

At least you know you carb is nice and clean inside, beavers are smiling all over the world

Yes new CDI  needed , i would also recomend new AC regulator as i think your voltage its little bit higher than it should be ,
http://www.bajadesigns.com/ProductDetail?ItemNumber=122002
this is a heavy duty one  that will last forever , or try ebay for a nice OEM one .



New fuel mixture screw , clean your air  filter, clean inside the airbox + install the backfire screen    , check the oil level  ,...
and start using both wheels  

Mad Frosty wrote:Yes new CDI  needed , i would also recomend new AC regulator as i think your voltage its little bit higher than it should be ,
http://www.bajadesigns.com/ProductDetail?ItemNumber=122002
this is a heavy duty one  that will last forever , or try ebay for a nice OEM one .



New fuel mixture screw , clean your air  filter, clean inside the airbox + install the backfire screen    , check the oil level  ,...
and start using both wheels  

airbox and backfire screen will be hopefully sorted tomorrow if i am out of the doghouse
we must of made a better connection on the cdi when we put it back on as the bike performed good on the way home, it was a fun ride back in the dark(minus terrible headlight)
still i bet i am the first person to have 385kph and there xr speedo, satnav wasn't so optimistic though, that said something else
i was just trying to preserve the front tyre

damn it, looks like i got outbid on the only cdi on ebay

anybody got any idea's were i might be able to grab one?

The XR400 CDI will work as well 2640 and 2740 if i remember it correctly , 2640 supouse to be better .

Hurry before its too late
http://www.ebay.co.uk/itm/HONDA-XR650-XR-650-02-03-04-05-06-CDI-ECU-/161404232990?pt=UK_Motorcycle_Parts_13&hash=item259471251e

I would just like to say thank you to everybody who has helped me out with this problem, it looks like it was not the carb(even though it needed re-jetting/servicing) or the cdi(even with a dead pin).

after all the money and time i have put into solving this problem and with the help of Frosty it turns out it was the trail tech vapor speedo and they way the previous owner had wired it in

been out for a few blasts about on it since i unplugged the trail tech vapor and the problems have vanished, now i just need some front & rear wheel spacers for the standard wheels so i can get the knobbly's on