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The TTR250 FAQ web pages -> TTR250 -> Carb stuff -> 1/3 - WOT Issue
Post Info TOPIC: 1/3 - WOT Issue
Gauguin


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1/3 - WOT Issue
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Hi

 

Im having a bit of a mare getting my '06 blue OE dialled in right, I've scoured these pages plus some others but can't seem to find the answers so I'm reaching out...

 

The bike is running stock exhaust and un-modded air box with stock filter. It came to me with 50 pilot and 147 main which I believe is standard for UK bikes. 

I'm at sea level

It idles fine and on steady throttle will get up to about 1/3 open before it starts bogging down... I can give it WOT to get through this but then when at higher RPMs the bike lurches erratically as though the fuel is rapidly cutting out and back in again.

Ive stripped the carb more times than I can remember since I bought the bike two months ago and found several issues which lead me to suspect that I'd fixed the problem.

 

Broken float pin post - repaired

Spring missing from diaphragm - installed

float level checked - good

all gaskets replaced as well as diaphragm

 

ive thoroughly cleaned everything out, jets have been reamed out with copper, check valves are working as they should, good squirt of fuel from accelerator pump into carb body.

No air leaks around rubber boot into engine casing, pet**** filters clean, fuel line in good condition. Air filter clean, new spark plug.

I've just fitted a new spark today, the old one was black and sooty (this may be from mucking about with different needle positions). I'll go for a spin tomorrow and check the colour of the new plug. 

 

ive had the needle clip in every position, bogs down worse when I go richer seems to run best when in the leanest position but by no means perfect. 

 

All i I can think to do now is fit a smaller main jet... does this sound right for an unmodded bike?

Best place to get jets in UK?  fowlers only stock original sizes.

 

Any other suggestions would be gratefully received  before I lose the plot entirely wink

Cheers,

Dan



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TTRfan


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Could the cam chain have jumped a sprocket and put the valve timing out? I have had similar symptoms when this has happened.

Brian



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Gauguin


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Brian

 

I've included some photos of the cam lobe positions when the fly wheel mark is aligned to the crankcase mark. TDC

Bear with me here but am I right in thinking that they should be level at this point I order to obtain a true valve clearance reading... Does this mean that the timing is out?

 

cheers

 

Dan



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TTRfan


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I think you have found the problem as the lines should be parallel to the head. See http://www.ttr250.com/Removing_Cylinder_Head/TTR_head_removal.htm for a photo.

Brian



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Gauguin


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Great to hear... I'll report back once sorted and fingers crossed all will be well. One of the lobes is looking a little worse for wear, visible in picture two. Worth replacing do you reckon?

 

Cheers for your help  

 



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TTRfan


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Not quite sure what I am looking for in the photo ref the lobe damage but new replacements are silly expensive and good used ones are like unobtainium.

Have you got a clearer photo or two?

Brian



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Gauguin


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Brian you were spot on! biggrin

 

I removed the the cam chain tensioner and shifted the cam sprockets so that the lines were parallel to the head, did all the checks you mentioned in your thread

http://www.ttr250.com/TTR250-valve-clearance-check-and-adjustment-how-to-guide.htm  

...and she's now running sweet. 

 

I've spent what must add up to days pickling my head with this... Bloody Amateur hour.

 

I've attached a zoomed in photo of the lobe in question... It just seems like a bit of the polished surface has disintegrated on the side face but the thing still has its integrity so I'm inclined to leave it be.

 

Thanks for the advice

 

Dan

 

 



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TTRfan


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I don't always get it right but glad the diagnosis was correct this time - and an easy fix biggrinbiggrinbiggrinbiggrinbiggrin

I think you will be fine with the camshaft....

Brian



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ttr steve


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Glad the Guru got you sortedsmile

Love this word - unobtainium biggrinbiggrinbiggrin



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