Mikuni Blues

[n16ht5]

Well, bummer. I had a TM34 on my 87 XR280R, and I couldn't get rid of all the bog no matter what. 👍 big surprise right?

so I slap the stocker back in and bog is gone.. but so is the top end power.🤣

I topped out at about 85mph with the Muckini. 13/44 gears. GPS speedo. power is good pretty much all the way till the motor is screaming at me.

Stocker carb... 75mphish. I need more room to get going, but it really slows about 70mph... takes a long time to get above that. getting up in the revs it really drops off the power after it peaks..

suck. I ride trails (single track mountains) but I like to ride trails FAST... well for a slug of a bike. I hate the bog, but I love the top end... what to do>? anyone got rid of their mikuni bog? should I go back to the kuni and suck it up or what? I might play around with the jets some more..

have 140main 40 slow in the stocker.. cant remmeber the kuni setup, I think I;ll try a 135 and 130 on tuesday or wed.

cobra exhaust (should I switch to trapp?)

gordo mods, ported airbox, uni filter, grounds bla blah blah

dont say get a xr600/650... too heavy for WA trails.

[paint it black]

ive no experience with the mikuni,but i have been doing a lot of research

into the keihin fcr,as i was given a used one a couple of months back,not got

it on the bike yet been cleaning it up,replacing bits,

seems a lot of the bogging problems experienced with those was from too

long a squirt from the pump,ideally they want about 1 second of squirt when

the throttle is opened,bench testing my fcr it would squirt for 4-5 seconds

which would have choked it up,

possibly something to look at,hope thats some help,

nick

[CHIEFCULPRIT]

Give this a read, it should help with the T34. I have got one on a 94 250L with R header and pipe, and very open airbox. My jetting is 50/200 and ride anywhere from sea level to 6000ft. I have a bog in mine only at the very bottom, only seems to be an issue when idling on the stand. Whats weird is now it seems to be running lean, I pulled the plug and it was ashy in color. I just haven't had the time to follow the steps in the attached link but 250machine and I have been throwing ideas around on this carb. Some people feel this is a 2 stroke carb only but I love mine, yes a pumper would be nice but I lack the cash flow.

http://www.iwt.com.au/mikunicarb.htm

[Baja trail Rider]

I use the 34 mikuni on our xr300s work perfect no bog .We got them from sudco,had to change every part in carb including slide,and needle from a 89xr250.Many hours to make that carb haul.We did not stay with the pumpers on the 250-300s went flat on top.Im sure somebody has the cure for that.

[unclewho]

Did you set it up right, sounds like maybe wrong jets on the mikuni or the pump on screw wasnt bottomed out

[n16ht5]

Sorry its a non pumper

Maybe ill play with it more, thanks for the link

[250Machine]

Hey Guys!

Chief, i got my jets!!! just swapped the right pilot 50 in, world of difference, bike screams all the way, little bog in the first 1/6 throttle, like you say idling on the stand or sitting idle.

i have the TM34 me and chief been going through how to get it to work better. his jetting settings really made me think of why i was at 27.5/180 with a bored over motor. and he ran a 50/200 on a stock L motor. now that i switched to 50/200 i notice a big difference i think i might give the 210 a try and see how it goes. who knows i might need a little more.

i would say you need to get some jets, 50/200 seems like a good place to start. i am at sea lvl and chiefs around 3k...i think.. i just dont think a 140 is enough fuel for the bike. i am starting to think a 200 isnt enough for mine if chief thinks hes running lean.

[CHIEFCULPRIT]

N16,

Go back to the Mikuni. Don't get talked out of it or into spending cash on a new carb (at least until you have gotten all you can out of the T34).

250,

Glad to hear it. It really is an awesome carb, do you notice a difference in the pull with the bigger jets? Seems like there is more top but I just run out of twist. I am running an original Gunner Gasser Throttle and it is smooth. Were you able to use that link I attached? I read through it and it makes total sense but never got around to doing the steps. I just did my valves for the 1st time myself and they were all in the mid range of specs, shocking cause they havent been adjusted for at least 7500 miles (really more but can't remember cause they were last done by honda in '97). Got a new front end coming so I will take pics of the swap and post.

Hey Guys!

Chief, i got my jets!!! just swapped the right pilot 50 in, world of difference, bike screams all the way, little bog in the first 1/6 throttle, like you say idling on the stand or sitting idle.

i have the TM34 me and chief been going through how to get it to work better. his jetting settings really made me think of why i was at 27.5/180 with a bored over motor. and he ran a 50/200 on a stock L motor. now that i switched to 50/200 i notice a big difference i think i might give the 210 a try and see how it goes. who knows i might need a little more.

i would say you need to get some jets, 50/200 seems like a good place to start. i am at sea lvl and chiefs around 3k...i think.. i just dont think a 140 is enough fuel for the bike. i am starting to think a 200 isnt enough for mine if chief thinks hes running lean.

[n16ht5]

Well I gave up on the mikuni... played around.. coyldnt get rid of the idle bog.

Cleaned out the keihin, put 125/40 set it to 2 1/4 turns

Wow.. runs like a dream. I was too rich before.

Next i took out the garbage in my pipe before the cobra.. there was a washer restrictor and some weird baffle thing..

Wow! Runs like a raped ape now! It pulls the front tire through 2nd gear no prob. I can't believe how much more power it has.. its unreal. The garbage in the exhaus pipe did the most

[n16ht5]

Well I gave up on the mikuni... played around.. coyldnt get rid of the idle bog.

Cleaned out the keihin, put 125/40 set it to 2 1/4 turns

Wow.. runs like a dream. I was too rich before.

Next i took out the garbage in my pipe before the cobra.. there was a washer restrictor and some weird baffle thing..

Wow! Runs like a raped ape now! It pulls the front tire through 2nd gear no prob. I can't believe how much more power it has.. its unreal. The garbage in the exhaus pipe did the most

[250Machine]

well sorry to hear you gave up. i just installed the 210 main jet on mine and its pulling even harder. i gotta do another plug chop test but i think its really close to perfect.

i have the cobra pipe too, i recently re packed it, sounds better. but i much rather have a supertrapp exhaust system. anyways have fun on your bike!

[n16ht5]

Mm do . do you have the 280kit? Hmm.. what kind of riding do you do?

I had lots of good top end, just poor off idle response/ bog. I really need the low end for the mountain trails.. maybe I need to go leaner hmm...

[n16ht5]

Yah my buddy has a trapp.. I want it. You should try pulling the junk out like I did if you havent

[CHIEFCULPRIT]

Baja TR sounds like he knows the carb inside/out, 250 has got a great handle on it and I am just left with figuring out the fine tuning. Did you read the link I posted?

Since your Mikuni is off the bike, tells us what jetting/needle/slide your running. Would a bog mean it's not enough gas or not enough air? Mine only happens when the bike is standing still and I snap the throttle, but all the trail riding never showed a bog. I feel my bike is running a tad lean on 50/200 jets but don't know where its lies bottom/middle/top. If there is any pop on decel it is very, very minimal to the point of non noticeable, but the plug shows some ash.

[Z06PSI]

Where is a good source for jets for this carb? I would like a wide range of jets if possible.

[CHIEFCULPRIT]

Sudco.com or just google Mikuni tm34 jets

[ATJ_Number_1]

jetsrus.com

[Z06PSI]

Thanks guys and I ordered some. They are not cheap are they........

[ATJ_Number_1]

I think they're cheap. If you paid more then $3 a main you paid too much.

[Z06PSI]

O.k. jetted the bike today and figured out how to start this TM34. 205 Main with a 35 pilot seems to be what I need. Was able to pull the front end on 2,3, and 4th with stock gearing. Choke on with 2 full compression kicks and then choke off one kick fires it right up.