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putting a keihin carb on my cr 250 07

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bought a keihin carburator wich came off a yamaha yz to put on my cr 250 2007 so now i´m wondering what to do with the TPS

just leave it unconnected ? the carb  has 2 connectors (1 connector= 3 wires black, yellow, blue and the other 2 wires black)

also wondering if the gascable from my mikuni fits or should i change it also ?

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Cable may fit, but earlier cable 97-2000 is slightly longer. Try the one you have, carefully routing it, it may be OK.

I initially did not hook up the TPS, but noted it did make a difference once hooked up. There is a complete description on how to do it on this forum, just do a search.

You will definitely like the carb., change.

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Send a PM to Hondamxracer.  He makes OEM quality cables to plug in the TPS.  The other plug doesn't need to be used.  Just plug the power jet with a set screw (which hondamxracer will provide for you if you want that with your TPS cable).  You can run it without the TPS but it does give the bike a little better off idle throttle response if plugged in.

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If I remember correctly if that carb has a power jet in it, it will require that you rejet the carb for it to work properly. The power jet adds fuel, so the main jet is smaller than a non-power-jetted carb would be. I did this exact same swap-I removed the Mikuni from a 2007 Honda CR250 and put a Keihin 38MM Air striker off a Suzuki RM250. It had the TPS and the power jet. I had to plug the port for the power jet, and then changed the pilot jet, and main jet, and then I was set. I ended up running a 42 pilot, 175 main but that's here for SOUTH Texas where it is 90-105 degrees most summer days. Your jetting may vary. I DID NOT hook up the TPS at all. I just left it attached to the carb, and then zip tied the wiring/connector up so that it would not get damaged. It was a night & day difference between the two carbs. Some will tell you that there really is not much to be gained by doing the swap.. You ride it after the swap and then please post back and tell us your thoughts on the switch.

Edited by Kawabuggy
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20 hours ago, Kawabuggy said:

If I remember correctly if that carb has a power jet in it, it will require that you rejet the carb for it to work properly. The power jet adds fuel, so the main jet is smaller than a non-power-jetted carb would be. I did this exact same swap-I removed the Mikuni from a 2007 Honda CR250 and put a Keihin 38MM Air striker off a Suzuki RM250. It had the TPS and the power jet. I had to plug the port for the power jet, and then changed the pilot jet, and main jet, and then I was set. I ended up running a 42 pilot, 175 main but that's here for SOUTH Texas where it is 90-105 degrees most summer days. Your jetting may vary. I DID NOT hook up the TPS at all. I just left it attached to the carb, and then zip tied the wiring/connector up so that it would not get damaged. It was a night & day difference between the two carbs. Some will tell you that there really is not much to be gained by doing the swap.. You ride it after the swap and then please post back and tell us your thoughts on the switch.

What year RM or KX carbs are the same as the that YZ carb?

 

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oke, thx for the info !! i´m trying to install it tomorrow starting whit a 178-45 jet and work my way down..  i leave the tps unplugged for now until i get more info or the right connection from this  Hondamxrace dude. hope i will not have issues with the gascable..

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I found mine by simply searching E-bay using 38MM Keihin carb.. Many different carbs came up but mine was for a 'Zuk RM250.  Be forewarned there are a lot of "NEW" china made knock off's. If the picture shows new vacuum lines on the carb, and a low cost, BEWARE. You are looking for a used carb, off a brand name bike.   Look at this one; http://www.ebay.com/itm/gasgas-keihin-300-pwk-carburetor-38mm-OEM-NOT-CHINESE-COPY-/371962733149?hash=item569ab4e25d:g:LmwAAOSwSypY~hI-&vxp=mtr

 

Edited by Kawabuggy

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installed the keihin 38mm airstriker yesterday and must say it was easyer then i tought.

it fitted perfectly between the air boot and reedvalve boot, i just could re-use my original honda gascable and connected the TPS..

keihin black = mikuni green, 

keihin yellow = mikuni yellow/blue

keihin blue = mikuni yellow red

airscrew 1.5 turn out.

 started at the first kick !

did not have the chance to drive it so jetting wil be for next week i guess.

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Come on Lorenzo we need a ride report man!!!!! You need to tell us how she runs!!!! I already know the answer because I have a crystal ball (and prior experience with this swap!).

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alright, finally yesterday i went to the track (sandtrack) to try out the new carb.. (i´ts on sealevel with a temp. of 23 celcius)

started with 178 main 45 pilot, needle on second and airscrew 1.5 turn out..

pulled the choke to start her up and pushed it back in from the moment its running just as i always do..

when i started driving and specially on high rpm it felt like the choke was still on so after 2 rounds  i stopped, let the engine cool down and checked the sparkplug (darkbrown)

so i changed to 175 main and 42 pilot.. it was a little better but on high rpm it stil felt a little like the choke was up.

checked the sparkplug and was lightbrown so to my opinion the way it should be.

because my daughter was driving also (with her cr85) i did not have the time to search further but now i´m wandering did i hook up the tps right ?

don´t think it´s the powervalve because it was fine before i changed the carb.. 

dont think i should drop the jets .. drop the needle ?

i´m no expert in carb tuning so i´m a little stuck here.. any suggestions ?

 

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Next step would be to raise the clip one notch and see if it gets better...if so, you know you're on the right track to leaning out the top end wot jetting. Can't provide much input as far as the TPS since the PWK I have came from a 1999 CR and doesn't have it. How was the idle after dropping the pilot down? And how about the airscrew turns? The reason I ask is because the pilot will have some effect on the entire throttle range as well with some bleed through of fuel adding to the mixture throughout. If it idles well and is really responsive in the 0-1/4" throttle range, it's probably just a matter of dialing in the needle/main at this point. 

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if i understand right you mean the clip of the needle ? so raise the clip means the needle drops a little..

when i dropped the pilot, the idle was also a little less so i also tryed airscrew 2 turns out instead of 1.5. it was a little better but not how it should be.

so my next step will be to raise the needleclip and see what it does..

thx for the info, i update as soon as i tryed it..

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38 minutes ago, Lorenzo2 said:

if i understand right you mean the clip of the needle ? so raise the clip means the needle drops a little..

Correct...raise the clip one notch which will drop the needle and lean it out.

when i dropped the pilot, the idle was also a little less so i also tryed airscrew 2 turns out instead of 1.5. it was a little better but not how it should be.

so my next step will be to raise the needleclip and see what it does..

thx for the info, i update as soon as i tryed it..

 

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He said he was already on the 2nd clip position on the needle. I don't think going to the 1st clip position is the answer. He has something else going on. If the plug is light brown, I would now be looking at the top of the piston for signs of detonation.

You really think the bike is running rich? When you first start the bike does it idle right down at normal RPM, or is the idle high for a few seconds before it slowly settles down?

Did you PLUG the power jet port? If you did not, and you are running a 175 main, it's going to be REAL rich. You must plug the power jet port with a set screw, or by some other means. I've heard of people driving in a lead weight with a punch and deforming it until it plugged the hole. Not the way I would do it, but I suspect in that low pressure setting, if done properly, it could seal the port. I threaded mine and used a small set screw with red Loc-Tite to permanently seal the port. If I remember correctly I plugged mine inside the float bowl so that no gas could get into the power jet circuit.

For testing purposes, just unplug the TPS for right now and ride the bike some more. It is not going to hurt the bike to ride it this way. So have at it and let us know what changes you experience.

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Not to hijack the tread, I just don't want to start a new one, so feel free to pm me even, but I'm just wondering if anyone else has had issues of the stock boots not sealing the enough? I have the 38mm screw-top keihin, and it seems to be a bit of dirt around the inner boot where it touches the carb. Wondering if anyone else has seen this.

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13 hours ago, Kawabuggy said:

He said he was already on the 2nd clip position on the needle. I don't think going to the 1st clip position is the answer.

I agree, and I wasn't implying that's the way to fix it, just that it'll help tell if he's on the right track to determining if it's too rich and leaning it further improves how it runs. I always shoot for ending with the needle in the middle clip position on a properly tuned motor. All things aside, and everything else being mechanically sound and within proper spec....you have to fine tune circuits, needle heights etc depending on altitude, temperature etc. as I'm sure you're aware. Remember, he switched to a PWK so there truly is no magic baseline that will be perfect just from suggestions. He needs to continue making small changes to verify the effects it's having. Only then can someone tell if the direction they're heading in is having positive or negative effects on how the bike is responding to those changes. :thumbsup:

 

 

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Slory I agree with what you posted. I was just thinking that if he is already on 2nd clip, there must be something else wrong. My guess is he has not plugged the power jet port, or somehow plugged it incorrectly,  and this is causing the bike to run excessively rich. If I remember correctly the power jet port will  be OPEN until it receives a signal from the computer to close. I don't believe his bike has the capability to run the P/J so his port will be open at all times causing a rich condition-UNLESS he has plugged it. Since the OP has not posted back yet, we will have to wait and see what he has done to correct it.

I hope you don't think i was attacking you as that was not my intention. I can be a little short at times but I assure you, none of it was directed at you. I agree fully with your assessment on making changes to figure out whether or not he is actually rich, or not. This should have  been a simple swap for him. If he were close I'd tell him to just bring it over and I would get to the bottom of it. I know this is not the right thing to do though as sometimes having to fight your way through something is the best way to learn. When others do everything for you, it kind of defeats the purpose of being self sufficient. OP-where are you? Maybe he's out riding... Yeah! That's it!

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No offense taken at all...I was just quoting what you pointed out and comparison to where the clip should ideally be...3rd position. It's all good brother, even if I disagree with someone, I never get angry or offended. Every bike is different and jetting isn't cookie cutter for two seemingly identical set of circumstances....we could give two suggestions and both still be wrong, lol.

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first of all i listen and apreciate all suggestions and will try several things and keep searching untill i get it correct.

no i´m not driving at the moment :-) i´m not so lucky to have a track in my backyard and here in Belgium they keep closing tracks because of nature, neighbours complaining or birds and butterfly´s breeding who can not be disturbed :-)

so i think it will be sunday before i can testdrive again but tomorrow i´l take the carb off and check it again and have a quick look at the reed valve altough i´m pretty sure its fine.

to be honest, i have no idea about this power jet plugging where and how should i plug it ? in my first post i added pics of the carb so maybe you can point it or discribe how to ?

last time i jetted a carb was in 1995 when i drove competition and back then it was a easy screw cap carb put a 178 main and 45 pilot and it ran great for the rest of the season :-)

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if you say inside the float bowl.. do i take the float out to get to this hole wich i should plug ? i´l open the bowl tomorrow and see if it makes me wiser..

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