TT-R250 Bogs downlow?

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#1
Well, my dad just rode my bike and he says that it bogs when you open up the throttle and I know it does it too, but just never really paid too much attention to it! What should we do in the carborator? Move the needle up one or the airscrew or what? Thanks
 

CRX

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#2
We have several TT-R's in our group and all of us are impressed on how cleanly the bikes carburate off the bottom. I would check and see if the accelerator pump is working correctly....CRX
 

Magellan

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#3
I've been having that same problem recently. In my case it's probably due to pulling the snorkel and baffle and changing the needle position (it's as rich as it goes)

I have been able to lessen the problem by adjusting the fuel screw and idle, but I think I really need to go with a richer main and raise the clip back to where it was.

Mag
 
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#4
It isnt so much of a bog, rather it is more of a cough! I open the throttle and it just sputters then it will finnaly pick up after some reving. Anymore help?:cool:
 
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#5
TT-R
Are you getting what I call a 'burble' at about 1/4 throttle? It may just be your mixture. Have you checked your spark plug? You might just need to clean your carb, over oiling your air filter can gunk it up too.
Strach
 
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#6
The airfilter is clean and the only thing that I could think of that could be the problam would be the carburator! It has been about a year since we opened it up. What should I do? Also I do have the baffel out but not the snorkle (doesnt do anything performence wise) Should I look into getting a UNI airfilter?
 

Magellan

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#7
Your problem sounds like my problem.

From idle, if I open it up all the way, the engine coughs and dies. If I open it up slowly and let the idle cliimb a bit, I can crank it open and it's fine.

Problem started after pulling the snorkel and baffle. I had to lower the clip 2 positions to keep the bike from popping at 1/2 throttle. I definetely noticed a gain in performance after doing this.

I pretty much elimiated the off-idle problem by messing with the mixture screw. I believe it is richer than stock (out farther), but not sure by how much. I set is as follows:

Set the idle screw for the slowest smooth idle you can get (this is proabably near the 1000RPM rec., but I don't have a tach).
Turn the mixture screw in until the idle gets rough, then back it out until it just gets smooth. I then went about 1/4 turn more for safe keeping (I'd rather be a but rich than lean).

THe problem isn't completely fixed. I think I need to go up a main and drop the needle to fix it or sure. I'll probably try that this weekend and will post my results.

BTW, you mentioned no change when pulling the snorkel and baffle. Is your bike popping more at mid throttle? Mine did. As I said, moveing the clip fixed that problem as well as delivered some performance gains. More air is only good if you have more gas to mix with it.

I suspect both are bikes are a bit lean off idle, and it may also be that the accel pump needs to be adjusted for the increased airflow. I do not have any experinece with those, so haven;t attempted messing with it...yet. If other fixes don't work, I may end up there.

Mag
 
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#8
Hello
mine had a 1/4 throttle burble when I moved the needle position one clip richer. I'm not sure the accelerator pump can be adjusted:think sounds like Magellan is on the right track. What kind of altitude are you at and what is the temp? What does your spark plug look like?
 

Magellan

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#9
I'm roughly at sea level with temps in the 60's.
I did a plug chop at full throttle and it looked good. I have an NGK chart that I got off the net and the plug matches one of the "good" ones, but it is a bit on the lean side.

The more I think about it, the more I am convinved that the transition between the idle circuit and the mid circuit is the culprit.
By raising the needle, the mid circuit comes on richer. Maybe too rich if the bike is coming off idle quickly. In other words, the engine isn't spinning fast enough to use that much fuel.

This makes sense as when I got the problem to go away completely, the bike started to rev high at idle once it warmed up, which indicates a lean condition. So leaning out the idle circuit fixed the burble, but wasn't a good solution as it had to be too lean.

Putting the needle back to stock and going up on the main should richen the upper half of the midrange circuit (where it overlaps with the main circuit) without affecting the idle circuit....

Stay tuned for my results...

Oh yeah, email me if you want a copy of the plug chart.

Mag
 
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#10
Have you considered replacing the stock carb with a 33mm Mikuni (Pumper) from Stroker?
As the guys from Stroker say “Get rid of the jetting headaches with the stock carb. For more performance and horsepower this carb is what should have been on this bike stock.”
I experienced a similar problem with the stock set-up. I was able to remedy the situation by replacing the stock exhaust system and carb with those provided by Stroker. I estimate an increase in house power by 5, not to mention 5 lbs weight savings. What a difference the changes have made....hey now it sounds like a 426!
 
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#11
Hi Fergy
Did the bigger carb give you any more top end? I have a Biggun system with the stock carb. I am really happy with it, It pulls so nice from the bottom and the midrange is great and then ... thats it! :( I know its only a 250 but will the bigger carb help ?
Strach
 
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#12
Strach,
The larger carb did improve my top end, infact it pretty much improved the whole range. The only down side was the cost of the carb. I believe it ran around $250-290 US. The carb comes pre-jetted and is designed for the TTR 250 application. I also modified the air box to allow better breathing which seemed to help. In fact I've gone as far as putting on almost all the aftermarket goddies Stroker offers for the TTR-250 (graphics, seat cover, removed spedo-cable, breather kit, removed headlite and replaced with YZ 250 number plate, frame guards). Doesn't resemble the stock machine anymore...gotta be different, just can't leave well enough alone. The carb really made the biggest improvement overall, well worth the investment. If your interested in Stroker aftermarket goodies you can find them at strokerspeed.com.
 
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#13
Fergy, How did you replace the front number plate with one off of a yz250? I have done the same thing but with just a flat universal front plate, and it is just zip tied to the bracks that holds on the light! Is this how you put yours on? Also, I think I am going to get a UNI airfilter and see what that does. The TT-R250 doesnt really have a good jetting capability:( Oh well. Couple more months and I will have enough for the yz125:p
 
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#14
TT-R,
I fabricated 2 brackets, one that connected to the top clamp and another connected to the front fender. The top bracket was fabricated out of a piece of 1/4" X 1" steel flat bar. Using my bench vise I was able to form the bracket into a "U-ish" shape which was then mounted to the top clamp. The bottom bracket was fabricated out of the same material, however it was just a flat piece. Using 1/2" nylon standoffs and longer screws (replacing the original screws (2x) which held the front fender to the fork) I was able to run the screws up thru the fender, thru the standoffs and into the fork bracket. I then used a few lock nuts to finish it off.
It all sounds a little confusing but it was really fairly simple to perform. Maybe I'll take a few photo and then post them. Geez, if there's enough interest maybe I'll fabricate a kit! Took about 2 hrs and approx. $5 to make. This does not include the cost of the YZ250 number plate.

BTW, the YZ250 number plate does not utilize any hardware to affix it to the bike. I just utilized the "plastic tabs" on the number plate, make the corresponding holes in the brackets and whalaaa.

Good luck
 
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#15
Yea, if you could would you post some pictures of the number plate and the brackets and a pick of what the bike looks like with all the goodies on it! Also, how do the stroker graphics hold up? I am still looking for a company that makes a good looking set of graphics!