Anyone out there have any info on tunning the circle m injectors? How about you old timmers that oval race tunned these things. Any help would be great. I found a set of 45's. Thanks Dean-o
toydoc
Member
Here is some info Dean-o.
Someone was nice enough to scan the info and post it sometime ago. I save them, thanks to who ever did post it the first time. Sorry I don't remember who.
Someone was nice enough to scan the info and post it sometime ago. I save them, thanks to who ever did post it the first time. Sorry I don't remember who.
WOW. Thanks Dean-o
toydoc
Member
Here's old one from the J A Pan Yamaha race team for oval racing fuel tank. Some of the wording is still in japanese.
RJH
New member
Nice manual – wow….
I’m not going to argue or reply to any negatives here – I’m telling you like it is! – See below
Hey – your best bet is to sell them. This is going to stir up the so called wizards…but.
They were invented by Kenny Roberts a famous road race dude. They were ingenious by design but why do you think production stopped only after a few years.
The good news is – we won some big time races here in Canada with them and the bad news is – we lost some major ones as well. Simply the huge mass of racers back then meant everything had to be 110% to be up front. The competition on today’s vintage stuff is no where near the speeds we had back then.
A bad working set meant we had to fight to stay in the top 3. A good working set (along with the other 1000 things required) would put our sled up front.
So– in the top 4 is not so bad I guess today. What happens is they forget how to atomize for some reason. If you really understand carbs – then it is a similar feel and sound of having too small of a main air jet in a VM. You could lean the thing out – but it just wouldn’t get crisp. It would seize.
How much HP loss???? We compensated by giving 1 more twist on the secondary. We got them for free and I HAD to run them so – I’d say we wet thru about 6 sets a season. You can’t beat the atomization (that’s what makes HP) of a float bowl carb. Even modern day injectors cannot make the same HP as a carb. Don’t flip out – new FI are probably the best bet overall.
I’m not going to argue or reply to any negatives here – I’m telling you like it is! – See below
Hey – your best bet is to sell them. This is going to stir up the so called wizards…but.
They were invented by Kenny Roberts a famous road race dude. They were ingenious by design but why do you think production stopped only after a few years.
The good news is – we won some big time races here in Canada with them and the bad news is – we lost some major ones as well. Simply the huge mass of racers back then meant everything had to be 110% to be up front. The competition on today’s vintage stuff is no where near the speeds we had back then.
A bad working set meant we had to fight to stay in the top 3. A good working set (along with the other 1000 things required) would put our sled up front.
So– in the top 4 is not so bad I guess today. What happens is they forget how to atomize for some reason. If you really understand carbs – then it is a similar feel and sound of having too small of a main air jet in a VM. You could lean the thing out – but it just wouldn’t get crisp. It would seize.
How much HP loss???? We compensated by giving 1 more twist on the secondary. We got them for free and I HAD to run them so – I’d say we wet thru about 6 sets a season. You can’t beat the atomization (that’s what makes HP) of a float bowl carb. Even modern day injectors cannot make the same HP as a carb. Don’t flip out – new FI are probably the best bet overall.
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dynofun
New member
- Joined
- Nov 14, 2005
- Messages
- 355
RJH do you still have a lot or pictures from back then?
RJH
New member
back then - I didn't care about pictures - only wanted to race - only have a few 
Notice the flat handling of the first pic - that was pro on a factory sled in Canada - the picture below was the year before in mod stock.
They gave me the first ever Jim Adema memorial award after that pro weekend race. Next weekend was the World Series - we had smoked the folks at Peterborough - but they (Yamaha) would not send me there.
Thanks
Notice the flat handling of the first pic - that was pro on a factory sled in Canada - the picture below was the year before in mod stock.
They gave me the first ever Jim Adema memorial award after that pro weekend race. Next weekend was the World Series - we had smoked the folks at Peterborough - but they (Yamaha) would not send me there.
Thanks
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dynofun
New member
- Joined
- Nov 14, 2005
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How do you remember racing against the Twisters in that 74-75 race year? I love the twisters but the way people talk today, they were the only sled out there.
RJH
New member
Yes..the Mercs were fast. One bad thing..can’t remember if it was 75 or 76 – but they had front ends busting – pretty well the entire powder puff class ( actually the chics then were very fast) was wiped out for the season after Peterborough with broken bones. If you lost control – there was a thick plywood wall to stop you –ouch. Nobody really bought much for more speed – we all made it ourselves.
You cannot believe the design talent back then – hundreds of factory sleds of every color in mod. A half mile oval would be packed in the infield with just sleds –no trailers allowed. In stock – most definitely – my second choice would be a Merc.
Most don’t realize. the speed back then. There were so many racers – like about 5 or more heats just to make the final – in 250, 340, 440 and 650. In stock, mod stock and pro. At radar runs in 1979 – there were 79 SRX’s stock doing over 100 mph. On the ovals – there was no runoff – just plywood. In 76 – mods were ticking just under 100 mph (on ½ mile shear ice tracks) with leaf spring skis.
I guess – watching the vintage stuff today – a 440 today would almost be as fast as 340 back then. Our race prepped 340 stock GPX was way faster than an out of the box GPX 440.
Our Yamaha ran away in 340 – and usually top 3 in 400 and 440 depending on the track length. Yamaha gave me a 440 a couple races in – and 440 was usually a win or top 3. We had the only Yamaha in the final.
You would think the T-Jets would be fast. The only sled that was physically faster (and we almost got beat) was when the factory T-Jet driver came from Quebec. He was ahead of us for almost 4 laps – but the Yamaha slowly reeled his light sled in and passed for the win at Peterborough. It must have been that they had only a single pipe. We just kept going at the same speed and about 150 pounds more.
On the Monday – they had a charity race – Jim Adema raced stock ( In 1976 I was the first recipient of the Jim Adema memorial Award) and the same thing – almost…. Jim and the other factory dude were battling – my Yamaha caught the T-Jets on lap 4 – just about to blow by them…and my exhaust spring broke!
74 was the same –mod stock again sponsored by Yamaha Canada East. The mercs were fast – as well as Doo’s and T-Jets. I made a ton of money with my 340 getting protested after wins in the 400 class, as I did the year before. Again –the only Yamaha.
76 they gave me a factory sled. The fields were huge – and fast. We were Yamaha east sponsored - they offered me either SRX 340 and 440 or the 75 factory sleds. We took the 75 sleds in June and my genius tuner and I rebuilt them. Things like arboly tracks (with a special gates rubber). We won by almost ½ a lap in 340 against ALL the other factories and 2nd and smashed in 440. We were working on Eagle River clutching on the 440. Jim was killed the week before. Anyways _ politics would not allow me to go to eagle River the next weekend – and I kind of lost interest.
The Mercs in 76 were rockets. The late Bud Lee and myself and some fantastic battles. His Mercs were sponsored by the Kohler factory in Toronto. What a smart bunch of tuners they were. We often went to the factory – just to look.
You cannot believe the design talent back then – hundreds of factory sleds of every color in mod. A half mile oval would be packed in the infield with just sleds –no trailers allowed. In stock – most definitely – my second choice would be a Merc.
Most don’t realize. the speed back then. There were so many racers – like about 5 or more heats just to make the final – in 250, 340, 440 and 650. In stock, mod stock and pro. At radar runs in 1979 – there were 79 SRX’s stock doing over 100 mph. On the ovals – there was no runoff – just plywood. In 76 – mods were ticking just under 100 mph (on ½ mile shear ice tracks) with leaf spring skis.
I guess – watching the vintage stuff today – a 440 today would almost be as fast as 340 back then. Our race prepped 340 stock GPX was way faster than an out of the box GPX 440.
Our Yamaha ran away in 340 – and usually top 3 in 400 and 440 depending on the track length. Yamaha gave me a 440 a couple races in – and 440 was usually a win or top 3. We had the only Yamaha in the final.
You would think the T-Jets would be fast. The only sled that was physically faster (and we almost got beat) was when the factory T-Jet driver came from Quebec. He was ahead of us for almost 4 laps – but the Yamaha slowly reeled his light sled in and passed for the win at Peterborough. It must have been that they had only a single pipe. We just kept going at the same speed and about 150 pounds more.
On the Monday – they had a charity race – Jim Adema raced stock ( In 1976 I was the first recipient of the Jim Adema memorial Award) and the same thing – almost…. Jim and the other factory dude were battling – my Yamaha caught the T-Jets on lap 4 – just about to blow by them…and my exhaust spring broke!
74 was the same –mod stock again sponsored by Yamaha Canada East. The mercs were fast – as well as Doo’s and T-Jets. I made a ton of money with my 340 getting protested after wins in the 400 class, as I did the year before. Again –the only Yamaha.
76 they gave me a factory sled. The fields were huge – and fast. We were Yamaha east sponsored - they offered me either SRX 340 and 440 or the 75 factory sleds. We took the 75 sleds in June and my genius tuner and I rebuilt them. Things like arboly tracks (with a special gates rubber). We won by almost ½ a lap in 340 against ALL the other factories and 2nd and smashed in 440. We were working on Eagle River clutching on the 440. Jim was killed the week before. Anyways _ politics would not allow me to go to eagle River the next weekend – and I kind of lost interest.
The Mercs in 76 were rockets. The late Bud Lee and myself and some fantastic battles. His Mercs were sponsored by the Kohler factory in Toronto. What a smart bunch of tuners they were. We often went to the factory – just to look.
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03viperguy
Moderator
you are a WEALTH of info, thanks for sharing, pretty cool to read about! my dad has a thunder jet 650, a 340 srx, and I have a 76 merc.... but only a trail twister 
keep the stories and opinions coming 
keep the stories and opinions coming