Mikuni 34mm Flat Slide Tuning

[frostyflammable]

I just received a 34mm flatslide Mikuni kit and really cannot find any online resources for tuning, especially where the mixture adjustment is and so on. I found the idle adjustment and the choke.

What I am used to on the round slide mikunis is the C-clip to adjust the mixture but the flat slide does not have it.

Anywho before I type for ages blabbing, anyone know of any pages or videos that could help?

Thanks,
Daniel

 

[bob58o]

Pictures or a model # may help.
TM34???

 

[frostyflammable]

I believe it’s a T34. Pics attached.

Thanks.

 

[KartFab]

Is it stock?
Standard Specs
Main jet (VM4/042)
Size 280
Pilot Jet (VM22/210)
50
Needle Jet
Q-2
Jet Needle
5FP17

I had to jet my TM32.

So in my limited jetting experience. I would say that you could "experiment with" the following jets:

200-220 ish main
25 -27.5 ish pilot
Needle jet, likely is TOO BIG, go down in size by one, keep the jet needle.

Now this could be really bad advice, because i dont have the same carb, 2mm makes a big difference in jetting.

So i do have the TM32 flatslide carb, and ran into some issues with jetting that resulted in my spending over $100 in jets and im pretty sure they use all the same series of jets and whatnot....

I would be more than willing to JET YOUR CARB for you!!! It would be on my honda gx390 with a.308 cam on T4 race gas, but it would get you in the ballpark of where you need to be if you are running it on gas with a moderate port job and stock size valves on a honda gx390 engine.

My only requirement is that you pay shipping to and from, and that you buy your own jets as i will ship it back to you in the same condition i got it (stock jets).

I only use genuine mikuni jets as knock offs and drilled dont perform the same.

EDIT
Ehh.,... welll since you live in dallas, if you want to come by my house, we can jet it there man, that is if you are putting this on a big block engine likea gx390/420. Free dyno session while we are at it haha, just shoot me a pm.

Also, i am putting out a public service announcement that I have no idea what air fuel ratio i need to set a small air cooled engine to. Most of the information out there is

12.8-13.1: for automobiles that have radiators etc.
12.5 for old school hot rods that have coolant
11.5-11.8 for air cooled race engines and/or under boost

so... I have gotten A/F reading of 11.1 on gas and it has excellent throttle response, and the plug is a little brown, not even black.... so in my opinion so far, 11.5-11.8 might be a good range to be in? I havent gotten any solid answers here, but it seems like some engine builders purposefully richen up the mixture to keep head temps down and keep it reliable. Just some thoughts. I can jet to whatever, but im not super experienced in what it should be "power wise" vs "longevity"

I could be wrong though.

 

[frostyflammable]

KartFab, the Mikuni is stock yes... however the Predator 420 will not be, I am putting on the stage 2 Kit from GoPower Sports however I have not decided on a cam yet, leaning toward the .308 since I want it to perform on the top end.

https://www.gopowersports.com/stage-2-420cc-hemi-predator-gx390-performance-kit

I live in Lewisville, TX... I put Dallas in there since most people know about where that is . I would not mind getting the 420 on the dyno once it is all buttoned up and see what kind of power it is putting out, I will def PM you for any help / meeting up since I am very much a noob when it comes to Mikuni carbs... heck I am not sure what most of the hoses attached to it are.

My 420 is still in its box, I need to take it apart soon just debating weather to send the crank to NR Racing to get it balanced. I want to get rid of the balance shaft figured balancing the crank may not be a bad idea.

--Daniel

 

[KartFab]

I sent you a pm, in the mean time you are going to want to clearance everything in the block before you send to NR racing.

I checked clearances in my gx390 block and man it was a really close fit, but I didn't have to clearance anything for the .308 cam (except counterbalance for rod). The intake and exhaust lobes came really close to hitting the crankshaft, but there was enough clearance there. I kept my counterbalance in, and had to clearance it from the dipper. The lifters were super close to bottoming (topping?) out as well.