TM 32 jetting

[Bngt]

Oooops. I am sorry, it should have been "From plug reading the conditions definitely do not look lean"
It was midnight here and I seem to have slipped.

This would not be so true if you are rich in the nj/jn combo already-but more likely that when the slide is closing it is richening the mixture and producing more power to pick up speed.

I think you could be right about this. Maybe the fat needle jet reverse the effect? Maybe when I get my P6s the behavior will change.

Maybe when I went down to P8 it became possible to use even larger MJ, but then the plugs tell a different story.

Then as strange as it was to reduce down to MJ 185 as strange it is to reduce from Q2 to P6 when others are running Q2s.

The bike is strong in bottom, mid and top so shifting to slightly smaller carbs to gain off pipe performance isn't really interesting, I'd rather shift down and keep her boiling or I'll cruise and then there is still plenty. Compared to MX a 32 for 180cc is rather small. Then I have read that some have had almost zero gain when shifting from 26-32. My motivation was to get a carb with a wide range of tuning options. It may sound funny when I am in the middle of confusion, but it is actually worse to have no alternative needles and needle jets.

I have a bike thread here http://www.rzrd500.com/phpBB3/viewtopic.php?f=5&t=8856

[pushstartrearset]

just for s&giggles i looked at Chapter 5 of the Mikuni Needle jet section. The manual shows a larger selection of jets. I see Dave picked a needle jet right in the middle of the 169 series or 169-PO. Looking @ the 389 series in my manual, the 389-P6 is right about dead center , just a notch leaner in between the division between rich and lean.

I basically counted how man sizes in either direction...pretty much dead center for both. Marks O2 is 5 notches leaner!!! wow, but I would gather the LC is a different motor.



Just was curious.

usiing my crazy logic, i would try a 320 main and 169-PO needle jet, but that is what i would do and then see where I am at. <--but that is me and i do crazy things. I figure if the 230 main and the 169-PO needle jet is okay in the RD, i would figure the 320 would be a good start point for the same needle jet in the RZ....you'll know right away if the 320 is the wrong one and I like REALLY positive signs, especially on the extremely rich side...makes it easy to figure out where to go in uncharted territory. Seems to be the way w/ VM28s and switching that over to an RZ from an RD w/o switching needle jets..but then you are switching...so who knows and start rich!!! that is IF you want to try that...besides, it will give you something to do..sort it out too quick and then what...find another beater to work on!!

[Badass]

Yes, I agree-the 32's are a good carb. I ditched my stockers almost immediately so I could tune. If I knew how to tune when I got the rz I might have left them on even though they are cumbersome to work with, heavy etc.

[Bngt]

...besides, it will give you something to do..sort it out too quick and then what...find another beater to work on!!

Sure, after all it is a hobby.
On the other hand I have two TZR to take care of and a 421 to put together and the GSXR is getting a TRE and healtech piggyback. So I might be able to keep busy anyhow.

I have ordered the Mikuni handbook.

I am curious to test even larger mains again, just to get a feeling for the difference. As you say it is very valuable to make big changes just to learn from.

I like the 32's but the Keihin 34 I got with the 421 kit looks fantastic and has a screw cap.

[pushstartrearset]

Are TSA pipes street or race? I would gather the race pipe doesn't hit till the higher rpms, whereas a street pipe should hit somewhere around 6k rpm starters.

[Headcoats]

TSA pipes are street but he has a few different versions.one that has a fatter midrange

http://www.rzrd500.com/phpBB3/viewtopic ... &hilit=TSA" onclick="window.open(this.href);return false;

[pushstartrearset]

Nice curve...smooth as a well tuned 4 stroke i would gather.

Q: When you say K&N, you don't mean this, right? ----> http://www.knfilters.com/air_filter/yamaha_rz350.aspx

If they are clamp-on or similar separate filters like this..and you don't have a tuned length or "space" between the filter and carb, you can have some crappy problems in the midrange. It would be worth your while to put some space between the filter and bell end for better running.

If you look at the Y-boot, each fork of the Y-boot is a specific length until it hits the large K&N that most of us run w/ the stock carbs. Since your TM32s are larger, this probably prohibits the use of the y-boot unless you heat and stretch it? or maybe you can get custom spacer tubes made that clamp and extra say 3 inches OR maybe the EXTRA LONG banshee separate K&N style filters.

Question is will they fit?...i would think the angled might be better as there looks to be even more length w/ the added rubber.

Anyone run these filters in the RZ or know if they fit inside the frame w/o problems?

sort of like this:
http://www.cascadeinnovations.net/store ... ept_id=103
They sell straight and angled style..mainly for 33~35 carbs, maybe a thin slip on ring made for you on the bell end if the filter is too sloppy?

[Bngt]

I think I need to repeat this; the bike is running very well without any stutter or strange behavior. The only remaining questions are could it run even better with fine tuning and am I safe? There is no "problem" to solve, just fine tuning.

This is what the filter setup looks like. I got the filters with the 421 kit I bought from Roger for the TZR.

[Bngt]

I found the text about identifying rich conditions through roll-off pick up. It is in Kevin Cameron's book "Classic Motorcycle Race Engines" page 279, a book I can recommend.

"In Ray Batterby's excellent reference Team Suzuki it notes that rider Frank Perris discovered that rolling the throttle off slightly produced better speed than full throttle. This requires some explanation. This is a classic symptom of over-rich mixture, which was surely intentional on Suzuki's part. Rolling off a bit drops a fatter part of the carburetor metering needle's taper into the mouth of the needle jet, reducing fuel flow. The result is a useful leaning of the mixture. By the mid 1960s every experienced rider would use this technique as a diagnosis for mixture richness; if the engine picked up revs in top gear as the throttle was closed slightly, it was too rich."

My understanding is that the behavior comes from the air inertia. When closing the throttle at first the air continues with the same flow before it is slowed down while the flow of liquid fuel, not being elastic, is reduced immediately creating a leaner mixture.
It also means that it is a dynamic behavior. You could very well have a fat condition at constant part throttle. What causes leaning is the sudden drop in fuel flow and less sudden drop in air flow.

[pushstartrearset]

I have a smooth transition through all my carb circuits. "taping off" your throttle and finding out where exactly this happens while riding for you can tell you if you have a problem. You shouldn't have a noticeable difference, transition should be relatively smooth like my bike is now. Otherwise, yes, you have jetting work to do. This could happen @ any part of the circuit from 0, 1/4, 1/2, 3/4, WFO.

They are mainly talking about WFO in this instance (racetrack)...you have a properly sorted needle, the main is too rich, when you roll-off, the mixture is correct (from running flat or uneven say on the mains) and you get this correction pickup. This could happen @ any part of the circuit from 0, 1/4, 1/2, 3/4, WFO.

I usually see things like this: falls off or flat (lean), revs but makes little power, surges on or off throttle or cruising, overheats (severe overheating and you can smell the heat!!). Rich: the bike hits a burble wall (revs no higher), uneven running, 4 stroking, more VIBRATION in mirrors(one way), lots of smoke, dribbling pipes and flanges (oily mix). EXTREME richness is the easiest...it will simply foul the plug quickly, then you have to put a fresh one in<....that is pretty much idiot proof

it can be a little confusing when the jetting is close..as the signs aren't as clear.

I'm still wondering about spec II's statement because if the needle were rich , rolling from 3/4 (start of WFO) to 1/2 (meat of the needle) would have the bike running worse, usually a flat burble way, uneven running and different exhaust note, you'd also have to constantly open the throttle to maintain consistent speed..<--so i'm still wondering about what he said. Your newest post highlights that.

lots to think about...plugs sure look very close. If you are happy w/i, then go w/i...it's impossible to compare how your bike is to another bike w/o being there.

watch your water temp gauge too...that will help in jetting also...when i was experimenting w/ smaller jets, I saw the temp also rise higher than normal...nope that's not it...this can also be used as a diagnostic.

[Bngt]

Current set up

1987 F2
Ported but with stock port timing.
Reduced squish same CR.
Kenny pipes
TM32
V-Force 4 reeds
Reed spacers
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 260
Needle jet 389 P6
Needle 5FP17 at mid notch
Pilot jet 27.5
Air Screw 3/4 turn

Water temp 70C
Altitude - sea level
Ambient temp about 10C now 25C in summer.

As was pointed out by several, the main jet was lean at 240. I have now P6 NJ and 260 MJ. It is possible to apply full throttle much quicker. I plan to test even bigger MJ until I get a negative effect. I also intend to test the needle in different positions and 30 PJ. It is not far off now.

[mboddy]

You could also fit a power jet.

[Bngt]

Yes, I have been considering a power jet, but I am not sure for what reason. Could you explain how you have been using a power jet and what benefits you have gained?

BTW I am now at MJ 290 and the bike works better than ever. I tried to raise the needle to check that the NJ wasn't too small at P6 but the effect was negative so I am back to middle clip. Might test even leaner.

[pushstartrearset]

This website explains their aftermarket powerjet. Go big and see if the 320 is even better! Powerjet allows you to drop 20 to 25 % on the main jet. So if the 320 does in fact become your main, a 20% drop in main jet size would be around a 260 (actually around 256, but who makes a 255?).

website: http://www.thunderproducts.com/thunder_powerjet.htm

[T.RexRacing]

To make it simple the PJ adds another circuit making the load on the others narrower and tuning the fuel curve easier and more precise.