A forum for owners of Yamaha TTR250 trail and enduro bikes!

TTRKYM · Member

Fitting a Mikuni TM32 and a TM33

pantheman · Member

Im also thinking in swaping the stock Y30P with a Mikuni TM33 because the TeiKei needs a rebuild badly but there doesnt seem to exist any rebuild kit ,Yamaha or aftermarket.
Im intrested to know if you finally make the mikuni work

-- Edited by pantheman on Saturday 28th of April 2012 10:34:51 PM

TTRKYM · Member

I must admit I was unwell when I tried the first time so I lacked enthusiasm some what.

I have since found how to get better access by removing the whole airbox. When I had it all out to adjust the needle it looked a tight but do-able..

When I get time I will give it another go and let you know.

davecambo · Senior Member

hi there again. im interested in finding out if it is worth it to change the stock carb out and install the 33mm pumper carb such as this type http://www.motorcyclecarbs.com/Carburetor_Kit_Yamaha_TTR250_P15343C1729.cfm

has anyone done this and what were the benefits if any?

cheers!

TTRfan · Super Guru

Hi Dave

We need some brave soul to try this upgrade out and report back!

A word of warning, I am sure that I read somewhere (Thumpertalk?) of problems installing that carb on a TTR cry

Maybe ask the supplier direct if they know of any problems?

Brian

TTRKYM · Member

Hi Guys,

Sorry I haven't had time to get back to it..

I rejetted the standard carb (raised the needle one groove) and this fixed my running problems. I found removing the rear subframe and air box is easy and looks like an easier carb swap...

However as I am now unemployed (Thanks Julia) I should get time for a play soon....

I will post here with pictures as soon as I can get to it...

Kym

-- Edited by TTRKYM on Sunday 22nd of July 2012 08:32:47 AM

TTRKYM · Member

RE: Mikuni TM-33 Mod

TTRKYM · Member

Well got to a good point today..

The airbox and carb removed...

The remote bracket needs bending outwards.. I used a shifter and bent it carefully...

See there now is a gap between the remote and throttle cables...

Installled carb from the rear, the airbox boot and clamp is a little too large. My fix was a trimmed large cable tie between the boot and clamp. Nice ant tight now...

Instead of buying another left hand engine mount I elected to modify the existing right one. The clutch mounting hole stays in use so all is good.

TTRKYM · Member

The carb installed.. One thing I noticed is for the fuel line the tank tap is 8mm and the old carb is 6mm. The Mikuni in 8mm so now a 8mm fuel line straight through..

No real ride yet but it started quickly, ran fine once it warmed up for a minute and idled nicely after I upped the idle a bit. I quick spin around the back yard showed no problems and plenty of poke..

TTRKYM · Member

So the modification list is as follows:

1. Throttle cable, there are two cables - open and close, the close cable needs to be longer (only about a cm) to suit the Mikuni. I bought parts to make a new inner cable - so two nipples and some cable. $3.80.

2. Engine mounts, the right one needs the diagonal bar removed to make clearance for the Mikuni. As per above picture.

3. The rear shock remote reservoir is too close to the throttle cables, I bent the mount to move the remote outwards away from the throttles.

4. Moving the remote out also made it closer to the bottom of the tank so I put a little foam between them just in case.

5. The air box rubber is loose on the carb mouth when the clamp is done up all the way, I got a large cable tie, cut off the locking end piece, trimmed the other end it to be just shorter than the clamp and placed it around the rubber between the rubber & clamp.

6. Tank is 8mm and old carb is 6mm, I replaced the fuel line with a length of 8mm fuel line all the way through.

7. The two old carb drain tubes are no longer needed so I removed them.

Oh yes and a new carb from - http://www.motorcyclecarbs.com/Carburetor_Kit_Yamaha_TTR250_P15343C1729.cfm

I will post a ride update after I give it a thorough test on the road/dirt..

TTRKYM · Member

I just took a test ride...

My bike has the air box opened out and a CRD muffler.

Idle and low down is good

Mid range is ok but starts to stumble as you close the throttle slowly..

Top end is full of missing and not good.

I would guess the air box and pipe have leaned it out and the needle needs to go up a groove and bigger main jet.

Seems to have plenty of go before it gets to the main jet...

TTRKYM · Member

I pulled the carb off to check the jetting and it's standard TM33-8012 and not re-jetted for the TTR250..

I have got a few ideas from the web but I have also emailed motorcyclecarbs to see what their settings are so I can adjust it here.

TTRKYM · Member

I pulled the standard carb apart to check jetting.

Standard main jet is 137, mine has a 147..

Standard Pilot Jet is (Service Manual 52) Staintune say 50, mine has a 50

The main also fits into the Mikuni...

TDVT · Senior Member

TTRKYM wrote:
I pulled the carb off to check the jetting and it's standard TM33-8012 and not re-jetted for the TTR250..

I have got a few ideas from the web but I have also emailed motorcyclecarbs to see what their settings are so I can adjust it here.

This is disappointing & contrary to the listing on their site.

I wonder if the 52.5/140 Mikuni jets that are suggested elsewhere as replacements for the TK would be a good starting place? I have heard (not sure) that the jet sizes don't necessarily "translate" in size from one brand to another, but the Thumpertalk listings are Mikuni parts. I'm not sure stock my carb is functioning properly & I'm interested in your results.

Thanks for the posts & keep them coming!

TTRKYM · Member

I have just replaced the jets and adjusted the Mikuni.

Currently I am running (different from standard) Main 145 (127.5), Lifted needle one groove (middle groove) and idle screw at 1-1/2 (1) turns out.

Float level still at 14mm as per factory.

Rides great plenty of pull, pulls clean from idle, revs out well but I think I can fine tune the top end as it may be a little out..

TTRKYM · Member

Just checked the roll-off testing method and my main is a little rich.

Not much of a problem, keep it cool under full power..

TTRKYM · Member

I just had the bike tested by the local Yamaha off road guru and he says the jetting is good enough to leave as is..

TDVT · Senior Member

Thanks for the follow-up! Sounds like it's running well.

TTRKYM · Member

Yep it runs very well. Might be a little rich so might look into changes if I need to pull the carb in the future.

Pulls so well now I wonder if I needed the bigger back sprocket now. Might see how it is starting in second on the road now.. Save first for the trails, if I can get time to ride it....

TTRfan · Super Guru

I just Googled the "roll-off testing method" as I hadn't heard of it before and found a really useful thread on jetting here. Apologies if this link has been referred to before.

Brian

TDVT · Senior Member

I was just re-reading your posts & wondered if you've gotten any more seat time & how the conversion has worked out?

I was also wondering if your had changed out the exhaust? Wasn't able to tell from the pictures.

TTRKYM · Member

Not sure if I mentioned the current bike setup..

I fitted a new Unifilter air filter, snorkle removed, holes drilled in top of air box (currently taped over), mate says try without the tape as i might fix the top end lean and give more power.

Previous owner converted a WR250F CRD Absolute Power II muffler to fit.

The car is busted so have been running around on the TTR and all is good..

If you have any more questions just ask..

TDVT · Senior Member

Thanks for the update. What was your final jetting & needle setting?

I am trying to sort my bike while the snow is still on the ground here & I am still rather dismayed with my TK & the lack of tuning parts available, which is getting smaller. I had a jet order from Partszilla (formerly boats.net) set aside a month or so ago & now half the sizes are "unavailable/discontinued", leaving only a few to try.

My bike was one of those that was stored for a few years & the whole fuel system was CAKED with crud & despite a few cleanings, it still doesn't seem right. So I'm considering the upgrade that you've made as also I'm adding an adapted WR pipe myself.

Thanks for sharing all your info.

TTRKYM · Member

In the TM-33

I am running Main 145, needle bottom groove and idle screw at 1-1/2 turns out.

TDVT · Senior Member

TTRKYM wrote:
In the TM-33
I am running Main 145, needle bottom groove and idle screw at 1-1/2 turns out.

Any idea what the pilot jet was/is?

TTRKYM · Member

I have not changed it so will be standard by tha attached link at - 1.1

http://www.mikuni.com/pdf/tm33.pdf

TTRfan · Super Guru

Fitting a Mikuni TM32 and a TM33

TT-R250M · Super Guru

RE: Fitting a Mikuni TM32

TTRfan · Super Guru

TT-R250M wrote:
I guess the only way to know this would be to try it at this stage.

Excellent idea Jarrah!!! That would be a great, especially if the resulting pics and report are up to your usual high standard biggrin

Remember this isn't a pumper carb whereas the TM33 is. My guess is that this will save fuel but lose out a bit on initial acceleration.

I think I have a Mikuni of some description on the bench so would be interested in getting install and jetting tips.

Brian

TT-R250M · Super Guru

That was my thoughts on the carb subject Brian.

I was not aware that it was the Mikuni TM32 WITHOUT the pumper. Somehow I don't think that this would be much of an upgrade from the reliable Teikei Y30P. I am still open minded about it though.

On the jetting subject

I could not be sure what throttle range the Mikuni jets work at unless I tested the particular carb myself. This would change the way the carb performs through the rev range. That said it should not be an ''alien'' in comparision to the standard Teikei carb. To get the general idea of jetting you can use the info that I have uploaded to my site HERE.

If you choose to ignore the red header pipe as an indication that you are running lean, you will not get the most performance or fuel efficiency from your bike. Provided that your ''anywhere near'' the right main jet, there is no way to tell if it's lean without getting the exhuast sniffer out (not the human type :). The spark plug reading can help to confuse this issue because if your pilot jet is slightly too big it will send wrong reading to the plug. Also if oil is allowed to enter the cylinder it will turn your spark plug black also, but this will be more of an ''oily'' black deposit. The other way is a lack of power, which is hard to tell because lean does go better through some of the rev range. If the jetting is not far off but you still have a suspicion that you are running lean, you can drop your needle clip position down (blunt end) until it runs bad. If it does not then you need to use a larger main jet.

Of course if your dead-set on having your exhaust glowing red, set it up this way. It would not be advisable though.

TT-R250M · Super Guru

To give some additional advice on the jetting, I will use my bike as an example.

My jetting is #52.5 PJ & #150 MJ with the jet needle clip position at the top setting- If I drop the jet needle clip position down (blunt end) two settings to the standard position it will splutter through higher throttle range (which means it is close to perfect). If I drop down in MJ size to the standard #147 main jet it gets hot/red at the header pipe, even if it the jet needle position is at the lower position (blunt end). It did however run fine, but it was slightly lacking in power.

To help with the main jet needle clip position

Provided that you are close to the specification needed for your mod's- Once you have found the ''roundabout'' setting & it runs without trouble, lower the jet clip position down (blunt end) until it you notice a slight splutter at higher revs. Then raise your clip position two settings. This will give you maximum power & fuel effieciency.

If you find that you are at the lower clip position & it still runs fine without spluttering, it suggests that you need a bigger main jet. On the other hand, if you are at the top clip position & it still splutters, lower the main jet size.

The pliot jet is easy- twin air filter + exhaust upgrade + snorkel removed or more = #52 or #52.5 or the equivelent (depending on elevation etc..). I am yet to try a higher pilot jet in mine so I am unsure if a larger PJ will help, but am VERY happy with my current set-up so this may not be happen any time soon.

TTRfan · Super Guru

More information from Peter Gray of Wilderness Wheels Morocco.

Re the adapter, the carb from XRs Only comes already fitted with an aluminium adapter at the airbox end (the engine side fits fine)

It was still a bit small for the TTR airbox, but though we couldn’t remove it easily, we just got another one made to make it the right size. The new adapter is a press on taper fit. I think if anyone wanted to import the kits to the UK, they could probably negotiate with XRs Only to have them pre fitted with an adapter to fit the TTR. We’ve bought lots of stuff from them in the past, when we had Hondas, and find them a good company to deal with.

TT-R250M · Super Guru

With no reply or reference to my jetting post I'm guessing that you either do not like it, you do not beleive it, it wasn't worth replying to or you just plain forgot.

Any way you look at it it suggests that it is not worth making reference to or you do not see it that way.

I really don't mind wasting my time writing all this jetting stuff, but why ask if you're not going to accept the facts? confuse

Maybe I'm just over-reacting (as usual) lol, so if I am, I take that back wink

All this info is not wasted though, I have uploaded it to my sub-domain archive after editing the bad English [however, its probably not much better on there]. evileye

ps. Just so you know, I do NOT upload anything that is not info of my own to my sub-domain. All information is my own, from reading this forum or info that I have learnt from helping others. I like this site for the learning side of things because it does not matter how much you know, there is always more to learn. wink There is always different ways of doing things, & different ways to look at things. I know you have poured your heart & soul into this website, as have others, so for that I am eternally grateful

TTRfan · Super Guru

Hi Jarrah - just opened the forum this morning and wasn't expecting to see myself being told off disbelief

I am really sorry if I have offended you. That was certainly not my intention and the very last thing I want to do!

I looked carefully at your posts but don't think the information applies to the Mikuni or have I misunderstood? confuse

This thread is really just about me passing on information from Peter at Wilderness Wheels on his first-hand experience of installing a Mikuni TM32 and using it for real in the mountains and sands of Morocco.

I have no argument with your jetting information and it is well argued and discussed on the thread here.

You know that I have admitted many times that I am not a carb expert and, personally, like to leave things as standard as possible. I therefore bow to others superior knowledge on the subject

What would you like me to do to put things right?

Brian

TT-R250M · Super Guru

Fair enough Brian.

I just did know what to think when there was no reference to my posts. I guess I was just over-reacting (again) lol, so I will take back what I said, if that's okay with you. wink

If it has an adjustable jet needle, the info should still help for the Mikuni. Results may vary from the Teikei, but the basic structure of jetting is the same. The jet sizes may change, depending on whether it has more than two jets.

All good Brian, no apoligy needed this end. I just hope you did not take offence to my post, if so I apoligize.

TT-R250M · Super Guru

I feel bad now, Brian has been nothing but nice & I'm just an arsehole at times lol.

On a good note, I just fixed my mates 1999 WR 400 that had many problems. After trying for days to get the carburetor running right, it turns out it is not worth fixing. I have now fitted as YZ426 carb so it goes REALLY nice! It starts first kick (against all odds) and runs well. bleh

He is impressed, as usual smile

-- Edited by TT-R250M on Monday 13th of January 2014 06:15:43 PM

partentyler · Newbie

Will a mikuni vm32 carburetor fit on my 2003 ttr 250?

TT-R250M · Super Guru

partentyler wrote:
Will a mikuni vm32 carburetor fit on my 2003 ttr 250?

If you are willing to make an adapter or know someone who can-Yes! Don't expect it to be an upgrade though....it has no fuel pump.

Jarrah

jsyoung88 · Member

carburetor size

TT-R250M · Super Guru

Hey JS and welcome to the forum.

The TTR250 Teikei Y30-P is 51mm intake side and 41mm at the airbox.

You would do well to check out these threads-

CLICK HERE

HERE

And HERE

Enjoy!

Jarrah

jsyoung88 · Member

Thanks buddy...appreciate the fast response

jsyoung88 · Member

Being the newbie that I am I have another question...is the 51mm measured from the inside or from the bolt holes?

TT-R250M · Super Guru

jsyoung88 wrote:
Being the newbie that I am I have another question...is the 51mm measured from the inside or from the bolt holes?

That is the OD (outside diameter) of the carb. The inside diameter would be useless to you as the carb goes inside the intake rubbers.

Jarrah

jsyoung88 · Member

Jarrah, do you know if the mikuni tm34 has a single throttle cable or a push pull?? Or can you buy an adaptive bracket to use the push pull throttle and not have to switch the cables?

TT-R250M · Super Guru

Seems to be a single throttle cable.

Not sure if you can buy a a bracket to convert it to push-pull type? confuse

This should help- CLICK HERE

Jarrah

jsyoung88 · Member

Got carb and throttle hooked up and now the bike is not getting fire...what are some things I can check or do to fix this?

TT-R250M · Super Guru

At a guess I would say that it is either too rich or way too lean.

Things to check-

Carb slide is returning all the way

Cable is not over-adjusted or sticking

Carb has good fuel flow.

Things to try-

Use starter fluid or petrol in the spark plug hole to see if it is a extremely lean condition.

Adjusting the fuel metering screw to 1 1/2- 2 1/2 turns out.

Question-

What jets have you got installed?

Jarrah

TTRfan · Super Guru

Jarrah's suggestions are good - lots more possibilities here.

After a rebuild it is easy to forget to connect stuff up - I have even managed to forget to fit the CDi!

A quick and simple check to see if fuel is getting through is to lean the TTR over and petrol should come out the carb overflow. Otherwise was the plug wet?

Brian

jsyoung88 · Member

Tried the suggestions of the gas in the spark plug hole and the bike is getting fire now but still won't start...anymore ideas on what might be going on?

jsyoung88 · Member

Not sure on the jets