Mikuni TM33SS vs. TM34 on a DR350

Hi to all. This will be my first post. I'm the proud owner of a 97 DR350 that I picked up from CL a couple of weeks ago. Paid 1,500 for it, and it only has 2K miles. It's mint (minus the fact it's a FL bike,and been left out in the sun too long). All original.

Here's a pic; hopefully the link will work, i'm not too tech savvy:


Anyhow, I just ordered a Mikuni TM34 to replace my busted up 33mm CV carb that some cowboy decided to tear into and "fix". Now I know why I got such a good deal on it. The emulsion tube was broke off, the plug on the float bowl was being held on by RTV, enrichment valve shaft was bent and plastic hex retainer is partially missing...and on and on. RTV around the perimeter of the float bowl gasket was a tell-tale sign!

Out of haste and hurry, I ordered a Mikuni TM34. The intake side is 58MM, head side is only a mm ID bigger, and the same OD, so I thought it would be good to go- it's the same dimensions as the CV carb. Now that I'm waiting on it to get here, I've discovered that it's set up for 2 strokes, and it will bog off idle. Supposedly White Brothers offered this carb with the correct jets, and it was a working combo for the 350. I've got patience, just not a whole lot of time. In hindsight, I should've spent more time on here reading, spent a little more money, and got the TM33SS pumper carb from the get-go. Even thogh the intake diameter is 8mm smaller, I could fix/modify/rig up some kind of BS sleeve to compensate for the intake hose.

Does anyone have the White Bros main/pilot/air jet numbers? How do I modify my new TM34 to work on my bike? Should I just send it back? It's probably a waste of time; it was a special order.

Thanks for your help. I'll try and post some pics real soon.

Good luck, buddy! Nice bike!

To my knowledge the TM34 is not a pumper carb, just a flatslide and it's built for a 2 stroke.

I doubt you'll ever get it run properly on the DR.

What parts on the TM33 are broken/bad?

To my knowledge the TM34 is not a pumper carb, just a flatslide and it's built for a 2 stroke.

I doubt you'll ever get it run properly on the DR.

What parts on the TM33 are broken/bad?

You can get them to work... but it will take a lot of dinking around. The pilot circuit will be the biggest pain. To me it is not worth investing the time into. You'll be without an AP circuit so the pilot circuit will have to be set up rich as will the needle circuit just to get the thing to respond decently. So your cruise throttle economy will go to heck in a hand basket if you want it to have any snap at all. :thumbsup:


Thanks for writing back. Forgot to mention my name is David.

Bob-The CV diagphragm 33mm Mikuni that was on it is basically destroyed. Another pitfall is it's impossible (from my looking) to find a rebuild kit for it. They wanted thirty something dollars for just the float bowl gasket; nevermind the fact that the float bowl needed to be replaced as well. On the back of the bowl, there's a round shaped plug that looks to seal an air circuit. How some jackass broke that is beyond me. I could have the termoniology wrong, but there's a brass tube that protrudes out of the carb housing, and runs the length of the float bowl. At the end, there's a a plastic arch cap that's meant to control fuel splashing so the jet below that has constant delivery...does any of this make any sense? It's been over 15 years since I've had a dirtbike, I forgot the correct name of it- at any rate; it's not even there. You can see where it was broke off. That isn't all, but it's enough for me to be on the hunt for a new one.

Thanks Rob, that's kinda what I was thinking. I figured it would be too much playing around with. If the starter wasn't in the way, it wouldn't be so bad to just drop the bowl, and do a quick jet change out, but I'd rather get it right so I don't have to keep jacking with it...I'll get obsessive/compulsive with it, never get it right, burn up the whole weekend, piss myself off about it, catch hell from the Mrs over my "attitude problem", and on and on. Thanks for the heads up ya'll. I got a TM33 flat slide pumper on the way. Wow- I can get a 4bbl Edelbrock 600cfm electric choke for cheaper than that Mikuni!

I guess I should also ask- is that flat slide pumper carb gonna have a vacuum port to send vacuum to the pitcock, or am I gonna have to just leave it on PRIME?

I don't think they're gonna give me my money back on that TM34. Do ya'll have any idea what cc 2 strokes run them? My buddy's got a YZ250- I wonder if it would work on his bike.

Thanks in advance- David.

Sorry, I thought you had a TM33 because of the title of your post.

If your carb has a have a diaphragm its a BST33

Youre not going to beat this price for a TM33SS-8012 pumper from Viper Racing, plus another $70 from Kientech for a throttle, cable, intake boot and the air box tube adapter.

Superior performance compared to the CV carb.

*Edit* I see you have a Electric start which will require an aluminum spacer so the carb clears the starter which Kientech also stocks.

I would order all but the carb from Kientech.... still a great deal and well worth it performance wise.

STAY AWAY FROM USED TM33 pumper carbs!




Edited by Bob Onit

Thanks Bob, that's really good information. I would've never known that I'd be in need of the spacer. It makes sense now. Glad I can order it now, knowing that I need it, vs. trying to mount the thing and discovering then. Talk about saving me some heartache!

So...does the flat slide have a vacuum port for the pitcock? Just leave it on PRI? What do you think?

So...does the flat slide have a vacuum port for the pitcock? Just leave it on PRI? What do you think?

No vacuum port on the TM33. You can run it on prime/res but most people simply replace the petcock with a Yamaha Raptor 660 manual style (on/off /res) petcock. Any Yamaha dealer should have one or be able to order one for you and you'll also retain your reserve function.

The diaphragms in the stock DRS petcocks usually fail eventually anyhow which can cause major problems especially if you're still running the stock BST33 carb.

Yamaha Raptor petcock, $14.86

Ronayers.com part number is 5LP-24500-01-00

Good luck! :thumbsup:

I have a TM34 that was on a DR350, the jetting is

30 pilot

170 main

6DH2 Needle

with I think an 'O' nozzle.

I never could get rid of the bog at low rpms's when I whacked open the throttle. If you rolled the throttle it was fine.

If you ignored the bogging at low rpm's the bike ran better with the TM 34 than it ever did with either the CV or TM33 (currently installed) It made more power, lifting the front wheel was easier. Also with the TM34 it was much easier to start, a light half hearted kick was all it ever needed to start the bike.

Overall the TM33SS is better, less headaches and more info availible.

It's funny to hear that I spent more money on the DR pitcock rebuild kit than the price of the entire Yamahammer pitcock.

I ordered everything I needed from Jesse. That is a super nice guy. Janet is nice as well. Those folks work some hours over there at Kientech. I think I'll just end up running the pumper carb, and give the TM34 to my buddy for Christmas. Word on the street is the flat slide is a newer design over the older traditional round slides, and would be the perfect carb of choice for a CR125 w/ a big bore kit.

Thanks so much for the help you guys. It's nice to get on these forums and talk to folks that know what they're doing, and have the decency to help poor slubs like myself- people they never even met. Thanks again.

Edited by farmfuel
incomplete sentence

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