Does the slow and main jet follow eachother?

[vsop-dk]

Hi, as the title says, Does the slow and main jet follow eachother?

Meaning, ive had the tm34-2 carbs delivered to me as part of the engine rebuild and the shop delivering this, thought that my exhaust were 44 ID wich they are, but didnt pay notife to the fact that I allso have some dyno inlets at the exhaust stud, so ID would be like stock...

Anyways, the tm34-2 were delivered with main jets at 250 the plugs were black with carbon. So Ive reverted the 250 to 190.

I know its a huge step down, but if 250 were adressing the ID 44 then 190 would be around stock.

So the question really goes to when ive changed the main jet, should the slow jet allso be changed at the same time and what size would that be to correspond to the 190?

Hope im not getting flamed for asking and getting thrown to the bin and asked to read e carb guide its good, but this is just a particular question that for the skilled peeps in here might be an easy aswer.. And yes ill be reading, just im slow at it

 

[XSLeo]

The TM34-2 carbs are not stock, so the carb guide doesn't cover them. Stock XS650 carbs were BS38's or BS34's.
There may be someone on here that has worked with the TM34 carbs. If so they might pop in and tell you more about them.
Leo

 

[5twins]

I've never heard of a TM34 so I can't be much help with that. What I can tell you is that carbs, all carbs, are a combination of several circuits that all work together, and in succession .....

Any one circuit influences the one next to it to a certain degree. Changes in one will "bleed over" and influence the one next to it. Sometimes that means changes are needed there too.

 

[vsop-dk]

XSLeo and 5twins, thanks for responding. 5twins the illustration is great as a reference... I see that the main is in the 0-1/8 end and could allso if too large cause faulty/carbon covered plugs..

If the bike runs great and doesnt carbonise the plugs and it runs great, then I migh be on my way.

Ill test and see and change the slow jet allso. Thanks

 

[chizler62]

A few things...if they're the carbs I'm thinking of. Is the choke a plunger or a lever type. If the lever type pulled up is OFF and down is ON. Seen this mistake before. Leaving it on thinking it's off.

The pilot jet is 100% always in effect. It's most effective to 1/4 throttle but still continues to always play a role in jetting regardless of throttle position.
Off the top of my head your car probably has a 50 pilot?

Important factor to remember flat slide smooth bore carbs have "air screws" not "fuel screws" so turning the air screw in with richen not lean it like a fuel screw.

If the low speed screw is on the engine side of the slide than its a fuel screw. If its on the air box side of the slide it's an air screw.

I'd put the 250s back in. That actually seems to be on the lean side already. I'd make sure the clips are in the middle "did they come with 3.3?" 3.3 needles valves are popular in those carbs.
Get it running and do an idle drop. If the low speed mixture screws have an effect then I'd start playing with the needle clips or shims. lowering the clip is raising the needle and richening it. Raising the clip and lowering the needle is leaning it. I'd mess with this before changing the main jet. If you can see a difference after the adj then you're in the ball park. Ride it and get time on it.

85% of riding is normally on the needles and pilots and not entirely on the main jets. The mains only come into effect once the needles taper off. Typically 3/4 throttle and up.

If you roll out of the throttle and get little pops it means you're too lean on the needle adj....typically. Not rich. People get confuse with lean fires and mistake them for being rich. You'll also notice a quick bluing or yellowing of certain finishes on exhaust.

 

[vsop-dk]

chizler62 thats a perfect write up. Thanks.. Kind of makes sense now that you put it in writing. Its air screws i have... and now they are 1.5 turn out..

The main jet were 250 now its 190... I can offcourse revert that...

The needle is 5FP17 at 3 clip

The plugs are Black with carbon, engine runs great besides the carbonised plugs and extreme kickback when trying to kick over.

Im not exactly sure, but the engine oil seems to smell a bit of gasoline...

Allso, perhaps a valid information, if I havent turned off the petcock, fuel will drip below the engine from the carbs, is that normal?? Thought they wouldnt let anything out...

Thanks

 

[grizld1]

Aw, for cryin' out loud! Woulds you guys who don't know please match your noise to your knowledge and resist the temptation to advertise your ignorance?

vsop, on the XS650, the TM34-2 requires very similar jetting to the VM34. Your jetting is far too rich. Right, depending on demands of the individual motor, you'll probably wind up with mains between #180 and #190. You need to do far more than just play with mains and needle clips. If your needle jets are the fat Q2's that Mikuni delivered in your carburetors, you need to change them out for P6. You'll wind up with pilot jets somewhere between #22.5 and #27.5. There should be no air correction jets in the intake bells unless some misguided person screwed them in there; Mikuni left the holes open and so should you.

As far as fixing your float system is concerned, read the Carb Guide. As far as float level specs are concerned, do your own homework; I don't do spoon feeding.

That's all you get. Order the Sudco Mikuni Tuning Manual and read it.

 

[Uhlaf]

Stop what you're doing immediately.

If you've got gas flowing from your carbs and into your crank with your fuel off you need to check your petcock and carbs for the leak. Gas in your oil is a quick way to ruin your engine. Replace your oil before you start running again.

 

[vsop-dk]

Thanks for the below, nice to get some info to Work with on top of the above.

If the following is in my shoppingcard would that be within specs?

Main jets: 185,190,195
Pilot: 22.5 25 and a 27.5
Needle jet P-6
Needle a 6F9 supposedly this is for a vm34 so could someone enlighten me here??


could you elaborate this? im not ignorant but English isnt my native language.

"There should be no air correction jets in the intake bells unless some misguided person screwed them in there; Mikuni left the holes open and so should you."

Aw, for cryin' out loud! Woulds you guys who don't know please match your noise to your knowledge and resist the temptation to advertise your ignorance?

vsop, on the XS650, the TM34-2 requires very similar jetting to the VM34. Your jetting is far too rich. Right, depending on demands of the individual motor, you'll probably wind up with mains between #180 and #190. You need to do far more than just play with mains and needle clips. If your needle jets are the fat Q2's that Mikuni delivered in your carburetors, you need to change them out for P6. You'll wind up with pilot jets somewhere between #22.5 and #27.5. There should be no air correction jets in the intake bells unless some misguided person screwed them in there; Mikuni left the holes open and so should you.

As far as fixing your float system is concerned, read the Carb Guide. As far as float level specs are concerned, do your own homework; I don't do spoon feeding.

That's all you get. Order the Sudco Mikuni Tuning Manual and read it.

 

[grizld1]

6F9 needles give good results in the TM34-2 as well as in the VM34; the 5FP17 that comes from the factory is suitable only for 2-stroke applications. And yes, the jet selection you've listed is where I advise you to start. For reference on general specs and procedures, read the Carb Guide, buy the Sudco Mikuni tuning manual, and go to www.mikuni-topham.de . Heed Uhlaf's warning! Good luck to you.

 

[5twins]

Here's an exploded diagram for your carb (download and save it). #53 is the air jet.

http://www.sudco.com/Diagrams323728/exptm.gif

 

[vsop-dk]

Thanks, ill go purchase this and yes ive talked with mikuni-topham allready and were summing up. Ill go read the Carb Guide aswell.. Just want this to run perfect.

6F9 needles give good results in the TM34-2 as well as in the VM34; the 5FP17 that comes from the factory is suitable only for 2-stroke applications. And yes, the jet selection you've listed is where I advise you to start. For reference on general specs and procedures, read the Carb Guide, buy the Sudco Mikuni tuning manual, and go to www.mikuni-topham.de . Heed Uhlaf's warning! Good luck to you.

 

[vsop-dk]

Thanks... ive allready got that browsing like an animal for tech stuff.. Thanks for the links though.

Here's an exploded diagram for your carb (download and save it). #53 is the air jet.

http://www.sudco.com/Diagrams323728/exptm.gif

 

[chizler62]

Aw, for cryin' out loud! Woulds you guys who don't know please match your noise to your knowledge and resist the temptation to advertise your ignorance

That's all you get. Order the Sudco Mikuni Tuning Manual and read it.

Feel free to point out what was so wrong with the above suggestions you feel justified to personally attack?

Posted via Mobile

 

[grizld1]

OK, here ya go. #250 MJ is far out of range to the rich side and you were ignorant enough to say it sounded lean to you; no mention of the NJ that's needed; no recognizable needle recommendation (WTF is a "3.3" Mikuni needle anyway?); and reference to the factory-installed #50 PJ as if it could possibly be used in a 4-stroke application. Those carbs come from Mikuni with generic 2-stroke jetting, and nearly every piece of brass in them needs to be leaned way down for 4-stroke use.

You ask me what's wrong with those recommendations? Really, are you delusional? If you insist on posting on things you don't have a clue about and strike a pose as Mr. Ace Tuner it's your right, but you can expect to get called on your bullshit.

 

[ippytattoo]

OK, here ya go. #250 MJ is far out of range to the rich side and you were ignorant enough to say it sounded lean to you; no mention of the NJ that's needed; no recognizable needle recommendation (WTF is a "3.3" Mikuni needle anyway?); and reference to the factory-installed #50 PJ as if it could possibly be used in a 4-stroke application. Those carbs come from Mikuni with generic 2-stroke jetting, and nearly every piece of brass in them needs to be leaned way down for 4-stroke use.

You ask me what's wrong with those recommendations? Really, are you delusional? If you insist on posting on things you don't have a clue about and strike a pose as Mr. Ace Tuner it's your right, but you can expect to get called on your bullshit.

LOL!!



vsop listen to grizld he co-wrote the carb guide and when he talks about carbs he knows his stuff. You have gotten more info than most would have.

 

[chizler62]

Give you I was thinking 250- 280 for 150-180 when writing. .....still, your ego feels it necessary for belittling people?
3.3 needle? Valve assy. I asked because I've seen Flat slides ordered for yfz350's with larger.
Asking "if you have a 50 pilot" it identify his carb is bad advice?
With egos like yours and a few others on here I see why the XS650 crowd gets no respect in the motorcycle community.

 

[ippytattoo]

Chizler it is not about ego it is about disseminating accurate information. If the inaccurate information is left as is and then someone else follows that information which adds to their frustration, where is the benefit to anyone but the poster of the inaccurate information? If you post inaccurate information and then challenge anyone who dares point it out and then claim a personal attack it is of no benefit to anyone at all. If you make an error in the way you word something or type something in incorrectly then just apologize and go edit your post to reflect the accurate information. As far as "the xs650 crowd getting no respect from the motorcycle community"I doubt that this little website has anything to do with how riders of one manufacturer look at riders of another manufacturer. In fact I can say from personal experience that where I used to live the big dog 1%ers had absolutely no problem with an xs rider like myself.

If you considered this a personal attack I apologize for trying to offer constructive criticism. Now back to the regular scheduled program.

 

[vsop-dk]

Luckily im not in the crossfire of this...

its valuable information and much appreciated response. Im on a steep learning courve and ill get at it... ive ordered the suggested parts

Main jets: 185,190,195
Pilot: 22.5 25 and a 27.5
Needle jet P-6
Needle a 6F9

from topham and will soon be able to get this thing rolling.. on the afterthoughts i should have gone for the vm34 carbs as there is much for compliance and read ups on those than the tm34 for xs650´s ... lectrons are allso high on my wishlist

have a great day out there.. and happy riding.

LOL!!



vsop listen to grizld he co-wrote the carb guide and when he talks about carbs he knows his stuff. You have gotten more info than most would have.

 

[ippytattoo]

The good thing is if you get this figured out and documented well it will give the xs community another resource for carbs. Hang in there and you will get it. Just knowing that the vm34 and the tm34 use very similar jetting is actually quite promising.