These look like power jets on the Roberts Yamaha YZR500 carbs:Badass wrote:They never used Power Jets on the Yamaha GP bikes, so if it was that good why is this? lol.
TM 32 jetting
Moderator: rztom
Re: TM 32 jetting
We race RDs, RDLCs, RZs, TZRs, TDRs and TZs at PCRA
Re: TM 32 jetting
Very cool, thanks for the pic. It makes sense that this is were it came from but I don't think they used them in modern gp 2t racers. Those are some funky looking carbs all connected together like.
Two strokes keep the mosquito's in check!!
1984RZ350 Bought with 2,600 mi. in 1998
SpecII Pipes, Complete engine rebuild, 30's, S. 1 Porting, Clutch, Self ported reed cages, T.D.R. reeds, Fork brace, Steering damper.
1984RZ350 Bought with 2,600 mi. in 1998
SpecII Pipes, Complete engine rebuild, 30's, S. 1 Porting, Clutch, Self ported reed cages, T.D.R. reeds, Fork brace, Steering damper.
Re: TM 32 jetting
2002 yzr500 .
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- yzr500_02_engine.9.jpg (88.62 KiB) Viewed 4494 times
"Let The Good Times Roll "
1985 rz350 .+4 stroke - banshee cylinder & head. wicked stroker pipes
std banshee carbs on VF4 reeds - 35 pilot , alba needle , 2.0 air jet , 410 mains with short foam ramair filters.
1985 rz350 .+4 stroke - banshee cylinder & head. wicked stroker pipes
std banshee carbs on VF4 reeds - 35 pilot , alba needle , 2.0 air jet , 410 mains with short foam ramair filters.
Re: TM 32 jetting
Mikuni TM and VM are old tech carbs.
A power jet is a low cost, easy to setup way to improve them.
The pic I posted shows them starting from half throttle.
Some more modern carbs have electronic power jets that start even lower.
For my road racers I normally have them starting about 2/3 to 3/4.
My initial tuning will be use power jet size 25% of main jet and reduce main jet by 25%.
For dirt bike I may start them from 1/2. Use power jet 20% of main and reduce main jet by 20%.
Do WFO plug chops to fine tune main jet like you would if you didn't have power jet.
A power jet is a low cost, easy to setup way to improve them.
The pic I posted shows them starting from half throttle.
Some more modern carbs have electronic power jets that start even lower.
For my road racers I normally have them starting about 2/3 to 3/4.
My initial tuning will be use power jet size 25% of main jet and reduce main jet by 25%.
For dirt bike I may start them from 1/2. Use power jet 20% of main and reduce main jet by 20%.
Do WFO plug chops to fine tune main jet like you would if you didn't have power jet.
We race RDs, RDLCs, RZs, TZRs, TDRs and TZs at PCRA
- T.RexRacing
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Re: TM 32 jetting
strutha wrote:2002 yzr500 .
Izzat yours????
There is only one difference between a madman and me. The madman thinks he is sane. I know I am mad.
Salvador Dali
Salvador Dali
Re: TM 32 jetting
"Why do you think EFI is so accurate? "
Because fuel injection can put a 'bend' in the fuel delivery curve like a carb can never hope to achieve?
Because fuel injection can put a 'bend' in the fuel delivery curve like a carb can never hope to achieve?
Re: TM 32 jetting
"Liquids don't compress thus meter accuracy is easy at a given pressure."
Does an emulsified fuel air mix behave like a fluid or gas? Or sumfing in between?
If the needle/needle jet and sometimes the pilot circuit meter emulsified fuel on most carbs I have seen, why so?.....if it is such an inaccurate means of dishing out fuel?
I'm assuming of course that an air jet in a given circuit emulsifies the delivery some what.
Does an emulsified fuel air mix behave like a fluid or gas? Or sumfing in between?
If the needle/needle jet and sometimes the pilot circuit meter emulsified fuel on most carbs I have seen, why so?.....if it is such an inaccurate means of dishing out fuel?
I'm assuming of course that an air jet in a given circuit emulsifies the delivery some what.
Re: TM 32 jetting
"It is difficult to meter precisely due to the ability to compress. The air jet is for fine tuning and is in the airstream to maximize accuracy. It is what feeds the needle jet air as well. Some set-ups do without it altogether,my YZ465 is one of those.
Why do you think EFI is so accurate? Liquids don't compress thus meter accuracy is easy at a given pressure. The air is metered by engine speed and throttle opening-both crude methods of metering."
These statements reminded me of two things.
The first is when I studied pneumatics and hydraulics during my trade cert.
Pneumatics and hydraulics are metered differently.(in a before/after sense).
The second is the media I remember reading when Mick Doohan tested fuel injection on his NSR 500 back in the day.
He reportedly chose to stick with the carbs even though Itoh if I recall correctly, used the injection probably to 'save face'
Why do you think EFI is so accurate? Liquids don't compress thus meter accuracy is easy at a given pressure. The air is metered by engine speed and throttle opening-both crude methods of metering."
These statements reminded me of two things.
The first is when I studied pneumatics and hydraulics during my trade cert.
Pneumatics and hydraulics are metered differently.(in a before/after sense).
The second is the media I remember reading when Mick Doohan tested fuel injection on his NSR 500 back in the day.
He reportedly chose to stick with the carbs even though Itoh if I recall correctly, used the injection probably to 'save face'
- T.RexRacing
- Posts: 1318
- Joined: Fri Nov 01, 2013 8:34 pm
- Location: back in the hills
Re: TM 32 jetting
As far as EFI accuracy I base my opinion on 20+ years of writing maps. It's much easier to isolate a fueling issue (if indeed the problem is a fueling issue) and correct with the aid of a 5 gas analyzer and dyno.
In the needle/needle jet emulsification is actually used to determine when the main jet becomes dominant and is very effective. There is a point where pressure differential is sufficient in overcoming the weight to pull fuel straight up from the main using needle taper (or lack of) to meter thus bypassing the emulsified mix because the needle jet can't supply fast enough.
As far as Mick and Itoh go EFI has advanced considerably since then.
In the needle/needle jet emulsification is actually used to determine when the main jet becomes dominant and is very effective. There is a point where pressure differential is sufficient in overcoming the weight to pull fuel straight up from the main using needle taper (or lack of) to meter thus bypassing the emulsified mix because the needle jet can't supply fast enough.
As far as Mick and Itoh go EFI has advanced considerably since then.
There is only one difference between a madman and me. The madman thinks he is sane. I know I am mad.
Salvador Dali
Salvador Dali
Re: TM 32 jetting
Trex, your twenty years of dyno experience is exactly why I have to read your posts twice, three or more times to gather the meaning from them.
I'm being obtuse deliberately to push the envelope on the discussion.
When the pressure differential is sufficiently low to create a situation where the fuel flow is 'lazy', is this not a time when the light weight emulsions comes into play? Is this what the D/J excells at?
I'm being obtuse deliberately to push the envelope on the discussion.
When the pressure differential is sufficiently low to create a situation where the fuel flow is 'lazy', is this not a time when the light weight emulsions comes into play? Is this what the D/J excells at?
- T.RexRacing
- Posts: 1318
- Joined: Fri Nov 01, 2013 8:34 pm
- Location: back in the hills
Re: TM 32 jetting
And I'm being obtuse to wrangle a specific question from you. I don't feel like typing a treatise on EFI. I'm a one finger typist and it takes forever.
By D/J I assume you mean Dial-A-Jet? I've not one lick of experience with them so cannot comment.
When pressure differential is low the acoustic waves in the intake tract are clipped and become square at the peak/valley. You can hear it with a load cell dyno. This is part of what activates the Thunderjet and Powerjet (an assumption on my part) as pressure differential is insufficient itself to pull fuel.
The needle/needle jet circuit "adjustable/tunable" via air bleeds,so yes that's when emulsified fuel is a key player. In fact I did indeed refer to this in my prior post. Same thing with the early pilot circuit. I didn't say it was useless just inaccurate,tedious to tune and subject to changing conditions. Especially if you lack dyno time. Track time is best used for other pursuits.
By D/J I assume you mean Dial-A-Jet? I've not one lick of experience with them so cannot comment.
When pressure differential is low the acoustic waves in the intake tract are clipped and become square at the peak/valley. You can hear it with a load cell dyno. This is part of what activates the Thunderjet and Powerjet (an assumption on my part) as pressure differential is insufficient itself to pull fuel.
The needle/needle jet circuit "adjustable/tunable" via air bleeds,so yes that's when emulsified fuel is a key player. In fact I did indeed refer to this in my prior post. Same thing with the early pilot circuit. I didn't say it was useless just inaccurate,tedious to tune and subject to changing conditions. Especially if you lack dyno time. Track time is best used for other pursuits.
There is only one difference between a madman and me. The madman thinks he is sane. I know I am mad.
Salvador Dali
Salvador Dali
- pushstartrearset
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Re: TM 32 jetting
So.
Who is going to be the sacrificial dickhead for the dial-a-jet?
Someone already done it?
I'd really like to try it eventually on the ole RD (looks like you mounted a flux capacitor from the future up dair). Make up all kinds of shi* at the local starbucks.
Who is going to be the sacrificial dickhead for the dial-a-jet?
Someone already done it?
I'd really like to try it eventually on the ole RD (looks like you mounted a flux capacitor from the future up dair). Make up all kinds of shi* at the local starbucks.
1984 RZ350L (U.S.) Old Toomeys, oil injected!, Y-boot K&N. loctite throttle cable holder on left carb!! , 410 mains, Dynojet needles 2.0 clip, #20 pilot @ 1.5 turn a.s., 240/512 p.v.
Re: TM 32 jetting
I have fitted them to two bikes but I have no credibility on here.
I also don't have the track miles/ experience to quantify my seat of pants findings.
Little is written about the D/J (dial-a-jet) that I can find on my Google searches so I do tend to stir the pot when I can to stimulate some conversation about them.
Dicks Racing has a service where they fit the D/J's as well as venturi splitters etc.
The D/J's seem to get the attitude of 'it's snake oil' more often than not and usually from people who have never even had one in the hand!
I also don't have the track miles/ experience to quantify my seat of pants findings.
Little is written about the D/J (dial-a-jet) that I can find on my Google searches so I do tend to stir the pot when I can to stimulate some conversation about them.
Dicks Racing has a service where they fit the D/J's as well as venturi splitters etc.
The D/J's seem to get the attitude of 'it's snake oil' more often than not and usually from people who have never even had one in the hand!
- pushstartrearset
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- Posts: 1339
- Joined: Thu Mar 17, 2011 4:20 pm
- Location: Vancouver, WA
Re: TM 32 jetting
I'd be more interested in any midrange gains on the street. I think the dial-a-jet (works at basically all rpms and NOT a powerjet! according to Thunder) would be the much better option over the thunder powerjet (meant for larger carbs). Very pricey at 239.00 bucks though. And why I would like a solid eval. before i even think about dropping that much on an external piece.tankslap wrote:I have fitted them to two bikes but I have no credibility on here.
I also don't have the track miles/ experience to quantify my seat of pants findings.
1984 RZ350L (U.S.) Old Toomeys, oil injected!, Y-boot K&N. loctite throttle cable holder on left carb!! , 410 mains, Dynojet needles 2.0 clip, #20 pilot @ 1.5 turn a.s., 240/512 p.v.
Re: TM 32 jetting
I think the price is probably the sticking point for most people. It's about the price of a new set of pistons isn't it?!!
But Iike i alluded to in another post I think, if it saves a melt down then it would probably pay for itself.
The Intelajet is the more evolved and robust product than the Dial-a-Jet in my opinion (I have fitted both BTW) and probably the better value.
Maybe someone like T-Rex could blag a sample product from Thunder Products and do some back to back dyno tests and publish some results on this forum.
But Iike i alluded to in another post I think, if it saves a melt down then it would probably pay for itself.
The Intelajet is the more evolved and robust product than the Dial-a-Jet in my opinion (I have fitted both BTW) and probably the better value.
Maybe someone like T-Rex could blag a sample product from Thunder Products and do some back to back dyno tests and publish some results on this forum.