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Post Info TOPIC: Mid RPM range bogs down???


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Mid RPM range bogs down???
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This is my first post, so go easy on me if I do something wrong.

 

I have a 1999 TTR250 that I have yet to see run correctly. cry

When my dad bought it, the throttle assembly was stuck, carb was completely gunked up, brakes were shot, wouldn't get gas through to the carb, and every part that was possible to rust, was of course rusted. I fixed it all myself, and I FINALLY got the thing to idle perfectly. The thing purrs nicer than a kitten biggrin! So I finally hopped on it and decided to take her around the block for a spin. All was well until I hit the mid range RPMs.

It bogs down HARD in mid range. Up until about 4-5000 rpm, the thing runs beautifully. Then at around 6000-8000 ish, it makes a deep-sounding "putt putt putt putt." But after that range, it works perfectly again confuse! I crank the throttle and it is amazing, I love the power and all that, but the mid range bog makes me unable to ride it until that gets fixed (because it slows down so hard it almost throws me over the bars. It feels like grabbing a handful of some front brake).

Jets are clean (I still have the stock jets), throttle needle is placed in the stock position (that's how I got it, I didn't put it there), and I don't think it can be spark because it works fine in low range, where I believe it would misfire more frequently, right? Also, I held the wire and cranked it, and it shocked the living crap out of me, so the spark plug is all in working condition, lol.

Any suggestions on what I should try next would be HUGELY appreciated. Ive been working on this bike for dang near 2 months now, and I'm starting to get a bit frustrated with it.



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Hey amjrulz1

You most certainly have a blocked diaphragm nozzle. It would also pay to check that it the diaphragm has no cracks and the two o-rings are not perished. Also check that your air jets are not blocked.

Checking the Accelerator Pump
Before dismantling the carburettor, it is advisable to check that the accelerator pump is working correctly. I should advise you now that petrol is not good for your eyes so be CAREFUL! The accelerator pump nozzle will have a hole (not the side shown in picture below) and it must be clean! To test this- remove carb and make sure it is full with fuel. When the throttle is applied it should squirt a nice stream of fuel into the intake. If it does not squirt (common problem), unblock the nozzle with a fine piece of wire. I use compressed air, fuel (or solvent), an old throttle or bike cable after cutting and splitting the strands apart and a pair of pliers to assist with holding the wire and prodding. Check that the one way valve is not blocked (shown below) by filling the carb bowl with fuel and pressing GENTLY down on the diaphragm, it should squirt fuel from the top of the check valve if working correctly (be careful as it could squirt fuel in your eye or shoot the 'one-way check valve' across the room). Also check that your diaphragm is not perished, if it is it will have cracks or it will be hard and brittle. Use Rubber Grease to extend the life of the diaphragm and all O-rings.
553027_562393563794119_1622177328_n.jpg
 
 
Enjoy!
Jarrah


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Thanks so much!
Ill check that when I get the chance tomorrow. I actually got a new diaphragm and those 2 little o-rings from a yami dealer, so I know theyre good. But I haven't cleaned out those, I don't know what I was thinking!
Ill check back and let you know if it works tomorrow, and thanks again!

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Well, I couldn't wait, haha! I tried it tonight and it totally worked! Dude, you are the best!!! Thank you so much! The only thing left is cosmetics and that bike will be perfect.
Thanks again.

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amjrulz1 wrote:

Well, I couldn't wait, haha! I tried it tonight and it totally worked! Dude, you are the best!!! Thank you so much! The only thing left is cosmetics and that bike will be perfect.
Thanks again.


 No problems amjrulz1, glad to help 

Jarrah

 



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