TM 32 jetting

[Bngt]

Cookie? May I ask which needle jets and needles you are running?

[Badass]

Do some plug chops, or else you are just pissing in the wind! The needle jet is the more difficult to get right imo so go out and hold it 1/2 to 3/4 under a load as much as possible. Put your fastest girlfriend on pillion and let er rip.

[Bngt]

Today I increased MJ first to 210 and then to 240 with great improvements.
It seems like I had too big needle jet and then when I reduced main jet it it helped the situation and I went all the way down to 185 but it became obvious that it was rich at part throttle.
Now with a smaller needle jet (P8) and needle in lowest position I get improvements as I move up with main jet.

From a driving perspective it seems just perfect. It needs to be on the pipe to take full throttle but I guess that iis as it should be.

I have also retarded ignition a bit.

Now I guess plug reading and perhaps a dyno run could help me with getting the details right.

[Bngt]

Current set up

1987 F2
Ported but with stock port timing.
Reduced squish same CR.
Kenny pipes
TM32
V-Force 4 reeds
K&N

Zeeltronic
1000 18
1500 20
3000 24
4000 25
7000 25
8000 22
9000 17
10000 14
11000 11
Powervalve
4300 0
8100 100

Main Jet 240
Needle jet 389 P8
Needle at top notch (leanest)
Pilot jet 27.5
Air Screw 1 turn

[T.RexRacing]

When tuning fuel you should begin with the pilot/screw circuit and work your way up to the mains.

Hmmmmmmmm...........................

[pushstartrearset]

Now with a smaller needle jet (P8) and needle in lowest position I get improvements as I move up with main jet.

From a driving perspective it seems just perfect. It needs to be on the pipe to take full throttle but I guess that iis as it should be.

I have also retarded ignition a bit.

I think you still have some leaning on the needle jets to do and accordingly the main jets will go up. loading up on low rpm rollon ..I mean you had to run your needle at the LEANEST setting..should tell you the direction you have to go...LEANER on the needle jets!!. (unless of course the bike runs worse) The tricky part is the needle / needle jet combo!! is it 230 or 320 depending on needle / needle jet combination? (cookie / Dave 210 to 230)---> Mark 320) and you have another choice for needles!!....you do have a load at low rpm (almost lugging it) like badass said, sounds to me like rich. I think you "got it" as when you start to lean the needle jets, the main jets go up. MBSTeve mentioned that the TM28s never work good out of the box and you have some leaning to do to make them work.

Again reference 2StrokeWorld, see my link in the previous post and pick Mark's brains. This could be a long process for you if you are many sizes rich on the needle jets. I've wasted a lot of time sorting my RD400 w/ R5 carbs, but now i've put LOTS of miles on it now it is sorted.

Or maybe cookie will PM you his secrets.

Just as in the RD, changing from bleed type needle jets to primaries and possibly? a needle change are going to alter main jet size or going from stock RZ carbs to just changing to Dynojet needles...see what a big jump that is! stock 230 main to a 410/420...<--example.

Do plug chops in 3rd gear...a little safer than the dangerous 5th and 6th gear.

good luck!

[Bngt]

Yep, I have ordered P6s. It makes sense to reduce until it is possible to run the needle in a more mid position.

Then I am wondering how much the needle position is affecting when the shift to main occurs.

It seems like there is quite a bit of overlap between needle jet and mains. I was expecting that once on full throttle the effect of the needle yet would be insignificant.

Since the different circuits overlap it is not really meaningful to talk about starting in one end or the other. I have read others suggest to start with the main jet and work downwards. My view is that to find the best combination one will always have to iterate anyhow.

I actually think this is interesting and not frustrating. Making test runs with different set ups and feeling the difference is very educational. I hope my honest sharing of success and failure is useful for those of you want to try setting up your carbs yourself.

[pushstartrearset]

MIkuni recommends (along w/ terrible T-rex!!) to start @ the , then work your way up (this of course w/ a ballpark main jet, but we don't know that!! yet). Since you can do a plug chop at any throttle position (key is holding it precisely there and then killing motor immediately, coasting to a stop...on the stand , you don't have to do this!). Try this first. put a fresh set of plugs in, let it idle w/ a fan in front of for at least 5 minutes, then let the bike sit on the stand just idling @ zero throttle for a couple minutes. You can put a fan in front of the radiator if you like.

Pull the plug and then see what you got. ZERO throttle is ALL pilot...could be a quick easy test for that circuit..and then of course the real world test of pulling out from a dead stop, stuff like that.

siince it will be idling at that throttle position for a couple minutes you'll get a pretty good idea if it is close or not starting w/ the pilot circuit.

yes there is quite a bit of overlap. and this is where things can get confusing if you are somewhat dimwitted like me...eventually through $$$ i figure it out.

spec II (Gary Shumake) on needle clip position (found this in my saved e-mails): "The only way to determine the proper needle position is to try it. At about 60mph and 7,000rpm, hold the rear brake and roll the throttle from 1/2 to 3/4 to full throttle and back and forth. When the needle is too rich, it will pick up when you go from 3/4 to 1/2. It feels like the throttle is wired backwards." MIkuni also mentions that the needle can indicate where you need to go if the needle jets aren't quite right...your case all the way lean on the needles...lets try a step leaner needle jet and see what happens...if in fact the 1st clip was right, the leaner needle jet will run worse...if it runs better, keep going this way (leaner) until you achieve a negative result and go back to the previous...you get the idea. Mikuni says the leanest possible (is the best for overally running, but not too lean, you get the idea).

Or you could take a risk, call Mark/Cookie monster? cookies! and HOPEFULLY his/their settings are right first try and you save all that time, BUT a step by step leaning is safe and good method starting from rich, but CoULD be expensive...

[Bngt]

Yes, I have read that racers found out that backing off from full and getting more power was a sign of too rich mixture. In the end I think you need to get a feel for it.
I also read that with a well designed dome, squish and reasonable CR you can lean out and go beyond max power and feel or at least measure the power decrease before getting into dangerous territory.

Pilot and air screw is quite easy to get right once you know the characteristic.

[cookie]

The bike I'm running TM32s on is a race bike so either 100% on or off throttle, I've never optimized the needle and probably won't bother unless I run those carbs on a street bike. That said I have my notes in the trailer, if there's less rain here tomorrow I'll probably get outside to have a look.

[Bngt]

Thank you Tony.


This is what the plugs look like after 2km full throttle:

Left:


Right:

[Bngt]

...and this is half throttle:

[T.RexRacing]

It looks like you can get away with a couple/few more degrees advance WFO.

How hot is the engine when you do the chops? What you seek is a nice ring around the base of the insulator where it meets the steel down inside.

I use something similar to this for reading plugs.


Some guys (me) cut the steel from the insulator like this to get accurate readings.

[Bngt]

Is WFO the same as WOT?
I googled but what I found wasn't printable.

I had 70C water temp.

I should get me one of those lamps.

Yes, I am considering chopping the plugs, but since they are so dark I thought I am not yet on the border.

If you look closely at the ground electrode there is a small grain. I was worried that it could be a sign of detonation. I wiped it away and the next time around it wasn't there. It didn't look metallic either, more like soot.

After having read about the benefits of late ignition to promote hotter exhaust gasses and better scavenging, I actually retarded timing a bit to get more overrun. Do you have recommendations for a good ignition curve? (I realize engines are different).

[cookie]

You have a zeel, right? I'd just move the whole curve 1 degree and try it.