montynormand
Member
I have never worked with these injector carbs. Heard tons of stories about how bad they are, how they cant stay tuned, how they eat pistons. And I've heard that when you get them figured out, they make tons of HP and are stable.....
I have picked up a pair off a GPX, and would like to play with them at some point. Got any insite and a list of do's and dont's to pass my way.
Any and All information will be helpful
thanks
monty
I have picked up a pair off a GPX, and would like to play with them at some point. Got any insite and a list of do's and dont's to pass my way.
Any and All information will be helpful
thanks
monty
RJH
New member
M's
hey...I'm here to! That 292 mod - I remember seeing Jim Adema's first 292. He built the first reed for it. The reed block was made from OAK. He smoked the folks at the time.
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Sell them on ebay!
Circle M injectors were originally designed by Kenny Roberts (famous Yamaha road racer) way back. The concept was fine with simple adjustments low speed and high speed – just screw it in until the thing screams.
The hose I.D. wall thickness and length were all critical. The units had to be used as a switch. In other words – they didn’t like being cruised with at mid range.
I can tell you this – if you had a set that worked – the engine made huge HP. The problem is – they didn’t work for long. When we raced – I’d say Yamaha supplied about 8 sets throughout a season.
Here is what happened to them, and why the accurate reference to wrecking pistons. They stopped atomizing correctly. An example in Mikuni world would be with the old VM that had changeable high speed air jets. It would be like using too small of a HS air jet. You could lean and lean – but the fuel would simply not atomize.
With the circle – when they stopped working – you could screw that high speed screw in looking for it to get lean. You could just barely get the sound on the stand – but put it under load and – another wrecked piston.
A bad set will still work to run it – you could trail ride all day – but you will not get that crisp maximum HP.
Many dudes think they have a good set - as they can run them all day....but I can assure you - they ain't runnin crisp.
hey...I'm here to! That 292 mod - I remember seeing Jim Adema's first 292. He built the first reed for it. The reed block was made from OAK. He smoked the folks at the time.
------------------------------
Sell them on ebay!
Circle M injectors were originally designed by Kenny Roberts (famous Yamaha road racer) way back. The concept was fine with simple adjustments low speed and high speed – just screw it in until the thing screams.
The hose I.D. wall thickness and length were all critical. The units had to be used as a switch. In other words – they didn’t like being cruised with at mid range.
I can tell you this – if you had a set that worked – the engine made huge HP. The problem is – they didn’t work for long. When we raced – I’d say Yamaha supplied about 8 sets throughout a season.
Here is what happened to them, and why the accurate reference to wrecking pistons. They stopped atomizing correctly. An example in Mikuni world would be with the old VM that had changeable high speed air jets. It would be like using too small of a HS air jet. You could lean and lean – but the fuel would simply not atomize.
With the circle – when they stopped working – you could screw that high speed screw in looking for it to get lean. You could just barely get the sound on the stand – but put it under load and – another wrecked piston.
A bad set will still work to run it – you could trail ride all day – but you will not get that crisp maximum HP.
Many dudes think they have a good set - as they can run them all day....but I can assure you - they ain't runnin crisp.
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montynormand
Member
I have been following the Circle M thread on Vintagesleds.com BS sessions..... Dont know how serious I'll get, but would be fun to see a pair work at some point. Someone has got to have fiqured out a "patch" fix to get these to work by now
gpxsrxracer
New member
- Joined
- Jul 28, 2005
- Messages
- 70
Well if they dont work then why do people who win at Eagle river such as Francis Higgenbotham still use them? They will still work. yes, alot of them are junk but to a few guys who have been messing with them forever they can still make them run.
As far as making more power, not really, they are for throttle response primarly. Toydoc has an article somewhere where a normal Mikuni roundslide made more h.p. than an injector unit.
I will be useing the fuel injection with Alcohol next year to try out and I'll post if I can get the injection to work properly.
As far as making more power, not really, they are for throttle response primarly. Toydoc has an article somewhere where a normal Mikuni roundslide made more h.p. than an injector unit.
I will be useing the fuel injection with Alcohol next year to try out and I'll post if I can get the injection to work properly.
RJH
New member
gpxsrxracer said:
If they work they work well.
montynormand
Member
Fransis and I spoke the other day and he swears by them. Honestly I am jus t intrequed by them and want to see one work well
Ok. I'm totally confused. Why and how do they good bad. Is there a wear problem. I'm thinking about running them on my 77 440 srx and 76 340 srx vintage mod sleds. Why are these injectors so hard to use. I can understand why they are like a light switch, but what wears out and makes them go bad? Thanks Dean-o
RJH
New member
M's
Deanosmod
I’ve been making it sound like they just don’t work – like stop. They do still work well..if you like trail riding.
No wear out problem – they just stop working at optimum level – the key word here is – optimum level performance. This could be one weekend or 3.
I haven’t stated this before – (cause I just remembered) but a bad working set will get you into top 5 amongst very fast top level sleds of similar vintage. Probably first – if the others aren’t at optimum performance.
I think you need a taste of what they can do before you get what they are not doing. For us – to try and get a dead set to run at the level we liked – it would seize. If we set them just to run – maybe top 3 for some – so still OK.
Stick with Mikuni. Especially if the new oval tracks have lots of snow dust. I noticed the best performance from clean very fast ice tracks with the M’s.
Here is a clue – a new set was always good for Sat and Sun. It wasn’t till the next weekend or 2 that they quit working at optimum level.
REMEMBER - OPTIMUM LEVEL
deanosmod said:
Deanosmod
I’ve been making it sound like they just don’t work – like stop. They do still work well..if you like trail riding.
No wear out problem – they just stop working at optimum level – the key word here is – optimum level performance. This could be one weekend or 3.
I haven’t stated this before – (cause I just remembered) but a bad working set will get you into top 5 amongst very fast top level sleds of similar vintage. Probably first – if the others aren’t at optimum performance.
I think you need a taste of what they can do before you get what they are not doing. For us – to try and get a dead set to run at the level we liked – it would seize. If we set them just to run – maybe top 3 for some – so still OK.
Stick with Mikuni. Especially if the new oval tracks have lots of snow dust. I noticed the best performance from clean very fast ice tracks with the M’s.
Here is a clue – a new set was always good for Sat and Sun. It wasn’t till the next weekend or 2 that they quit working at optimum level.
REMEMBER - OPTIMUM LEVEL
RJH
New member
black john
New member
- Joined
- Jul 5, 2003
- Messages
- 24
m
i ran these on my srx 340,s and 440,s the only thing that ever let go were the fuel pumps. the only reson that thet sized pistons was becaues thy only have a two stage needls in the throtale body. (ie thers only an lw speed and wide open metering) when you hit the turns you had to blip the gas costantly this would keep the pistons alive even the out side temp would cause the lines to get harder and change the jetting 340 line lenth was 300mm. and we found that with the ijection we could run a lot more clutch. we also ran egt,s with these to get a good idea on how they worked. pumps had to be mounted below the moter and gas tanks had to be moded to bottem out let as well. they worked very well on the track but i would not run them on the trail as there is no mid range metering in them. they also came in two sizes 42mm for the 340 and 45mm for the 440 and also there are two pump *** eraly and late the eraly ones had a screw on cover and were rebulitable later ones were crimped on and not rebuildable. i still have one of my 440 sets and manuals.
i ran these on my srx 340,s and 440,s the only thing that ever let go were the fuel pumps. the only reson that thet sized pistons was becaues thy only have a two stage needls in the throtale body. (ie thers only an lw speed and wide open metering) when you hit the turns you had to blip the gas costantly this would keep the pistons alive even the out side temp would cause the lines to get harder and change the jetting 340 line lenth was 300mm. and we found that with the ijection we could run a lot more clutch. we also ran egt,s with these to get a good idea on how they worked. pumps had to be mounted below the moter and gas tanks had to be moded to bottem out let as well. they worked very well on the track but i would not run them on the trail as there is no mid range metering in them. they also came in two sizes 42mm for the 340 and 45mm for the 440 and also there are two pump *** eraly and late the eraly ones had a screw on cover and were rebulitable later ones were crimped on and not rebuildable. i still have one of my 440 sets and manuals.
montynormand
Member
BlackJohn
would you be able to copy and mail me your manuels? I would love to learn more about these things. Kinda thinking I would like to try one on my SR292
thanks
Monty
would you be able to copy and mail me your manuels? I would love to learn more about these things. Kinda thinking I would like to try one on my SR292
thanks
Monty
RJH
New member
give up
I should probably just let this go – but…
You are correct about the installation and mounting. You have done your homework there.
I’m not sure, but it may say in the manual you should not to blip them. They should not be “blipped” according to the factory; it puts the extra stress on the pump parts. Probably diaphragms break down.
We could run “a working set” for 5 laps easy – pinned to the bar – except for entering the turn. Once they stopped working at “OPTIUM” performance – probably blipping would have helped – but it wouldn’t get you into first – unless at a “no fast people race”
By the why you are describing it – you were racing with a dead set. Not working at “OPTIUM” performance.
You are correct about two needles only – but we had no trouble driving around with the m’s. You could trail ride quite nicely – but I’d rather have a slide carb on. .
black john said:
I should probably just let this go – but…
You are correct about the installation and mounting. You have done your homework there.
I’m not sure, but it may say in the manual you should not to blip them. They should not be “blipped” according to the factory; it puts the extra stress on the pump parts. Probably diaphragms break down.
We could run “a working set” for 5 laps easy – pinned to the bar – except for entering the turn. Once they stopped working at “OPTIUM” performance – probably blipping would have helped – but it wouldn’t get you into first – unless at a “no fast people race”
By the why you are describing it – you were racing with a dead set. Not working at “OPTIUM” performance.
You are correct about two needles only – but we had no trouble driving around with the m’s. You could trail ride quite nicely – but I’d rather have a slide carb on. .
Roger Davis
New member
1) Circle Ms were not designed by Kenny. He did lots of good things, but not that. This idea may have started because of the Lectron carbs, not the same. The design was bought from a third party in a rough state, then adapted and refined for Yamaha by Mr. Hayata, a Yamaha engineer.
2) They are VERY sensitive to air bubbles in the fuel line. You MUST have a vented sump (like a big fuel filter mounted below the bottom of the gas tank, with a long vent hose coming out the top). This gives bubbles a place to go other than to fake out the pump. Also place the pumps no higher than just below the tank bottom.
3) During tuning, you must make sure to not lean the main screw too much, because if you do that, it will be lean on top - piston time.
4) I don't think they will flow enough to work for alcohol, but you might surprise me.
I'd like to give more info, but after 30 years, memory gets fuzzy. I have printed info .... somewhere... can't get to it quickly.
2) They are VERY sensitive to air bubbles in the fuel line. You MUST have a vented sump (like a big fuel filter mounted below the bottom of the gas tank, with a long vent hose coming out the top). This gives bubbles a place to go other than to fake out the pump. Also place the pumps no higher than just below the tank bottom.
3) During tuning, you must make sure to not lean the main screw too much, because if you do that, it will be lean on top - piston time.
4) I don't think they will flow enough to work for alcohol, but you might surprise me.
I'd like to give more info, but after 30 years, memory gets fuzzy. I have printed info .... somewhere... can't get to it quickly.
toydoc
Member
You sound like Roger Davis that use to work with Gordy back then. Don't remember if you are part of Davis Machine Co or working at yamaha back then, both.
Good to see you on here Roger
Good to see you on here Roger
Roger Davis
New member
Yes, that is me... Nice to come around a savor memories once in a while.