Install the app
How to install the app on iOS
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
975 w/twins
- Thread starter scoop
- Start date
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
7
alt, gears, carbs ect?
H
There are so many variables, target rpm and alt are huge as is how hard you want to load the engine. Loading the engine requires more fuel etc. etc. etc.
Gearing and making the primary and secondary work together is the key and there is at least 20 set ups that will net the same rpm. Its really has more to do with how much you like to tune to make it run perfect every ride out.
Most guys want a ball park pull and go set up, I want it spot on every ride
and will change a helix and or springs/ weights if needed twice a day to have it perfect.
My 990 preffered set up was 20/46 gearing, 265-310 primary spring, 64 gr
heavy toe weights ground down from 69s, 55/53 helix with red white cat spring in the second to softest setting. When I needed more rpm I would go 1
hole tighter and/or change to a 53.
This set up was at 8,000 to 10,000 ft shooting for 8250 rpm. I ran jaws twin race pipes and pulled 620 mains.
Mike
Gearing and making the primary and secondary work together is the key and there is at least 20 set ups that will net the same rpm. Its really has more to do with how much you like to tune to make it run perfect every ride out.
Most guys want a ball park pull and go set up, I want it spot on every ride
and will change a helix and or springs/ weights if needed twice a day to have it perfect.
My 990 preffered set up was 20/46 gearing, 265-310 primary spring, 64 gr
heavy toe weights ground down from 69s, 55/53 helix with red white cat spring in the second to softest setting. When I needed more rpm I would go 1
hole tighter and/or change to a 53.
This set up was at 8,000 to 10,000 ft shooting for 8250 rpm. I ran jaws twin race pipes and pulled 620 mains.
Mike
Last edited:
7
There are so many variables, target rpm and alt are huge as is how hard you want to load the engine. Loading the engine requires more fuel etc. etc. etc.
Gearing and making the primary and secondary work together is the key and there is at least 20 set ups that will net the same rpm. Its really has more to do with how much you like to tune to make it run perfect every ride out.
Most guys want a ball park pull and go set up, I want it spot on every ride
and will change a helix and or springs/ weights if needed twice a day to have it perfect.
My 990 preffered set up was 20/46 gearing, 265-310 primary spring, 64 gr
heavy toe weights ground down from 69s, 55/53 helix with red white cat spring in the second to softest setting. When I needed more rpm I would go 1
hole tighter and/or change to a 53.
This set up was at 8,000 to 10,000 ft shooting for 8250 rpm. I ran jaws twin race pipes and pulled 520 mains.
Mike
Mike did you choke the jaws twins down?
what carbs did you run.
Thanks
Shane
H
I run stock rack carbs bored to 41.5 and the jaws pipes were choked to 34mm
but I also run tight heads and straight 114 unical/rocket premix at 32:1
The race pipes I had jaws build for me come with 36mm outlets and were designed to run 8500 rpm, I only run them at 8500 to grass drag 8250 at alt.
They were a totally different pipe than the d- pipe, the d- pipe comes 38mm
and needs choked to about 34.5 to work well at 8000 ft
but I also run tight heads and straight 114 unical/rocket premix at 32:1
The race pipes I had jaws build for me come with 36mm outlets and were designed to run 8500 rpm, I only run them at 8500 to grass drag 8250 at alt.
They were a totally different pipe than the d- pipe, the d- pipe comes 38mm
and needs choked to about 34.5 to work well at 8000 ft
7
do you think 32.8mm is too tight on the d's?
I'm running cpc 48 with 540N mains and just looking for any input on combo. head are loose just above 60 on the squish on a 990
I'm running cpc 48 with 540N mains and just looking for any input on combo. head are loose just above 60 on the squish on a 990
When you guys talk about choking down, Is this done at the end of the stingers/muffler? Or is it where the pipes mount to the head?
Thanks
Mike
Thanks
Mike
pipes
I picked up some cpc 1150 pipes to run on my 975, I ran a sw single, but am porting the case and want to run these pipes. It a 05 efi kk. I figured I was gonna have to choke down the pipes but wasnt sure how much. Anyone run these pipes? What rpm should I be looking for???.....Im leary this is going to be a tuning nightmare!!!!!!clutching, choked pipes, timing, fuel........I ride 6000 feet and up, Rkt head, vented and gutted air box, ported (but not real extreem), 1000 pistons(975), Boyseen reeds. It runs well but there is more there that I want to try and get. So im gonna port cases, start w/2 degrees of timing, after I get it running from the porting and pipes. This is my plan for this season............
I picked up some cpc 1150 pipes to run on my 975, I ran a sw single, but am porting the case and want to run these pipes. It a 05 efi kk. I figured I was gonna have to choke down the pipes but wasnt sure how much. Anyone run these pipes? What rpm should I be looking for???.....Im leary this is going to be a tuning nightmare!!!!!!clutching, choked pipes, timing, fuel........I ride 6000 feet and up, Rkt head, vented and gutted air box, ported (but not real extreem), 1000 pistons(975), Boyseen reeds. It runs well but there is more there that I want to try and get. So im gonna port cases, start w/2 degrees of timing, after I get it running from the porting and pipes. This is my plan for this season............
7
When you guys talk about choking down, Is this done at the end of the stingers/muffler? Or is it where the pipes mount to the head?
Thanks
Mike
at the end of the pipe just before the stinger(s) you insert about a 1" piece of pipe into the end.
example if the ID of the end of the pipe is say 38mm the next choke will be 38mm outside and 35mm in side and if you need to go smaller you can slide 1 more piece into this and go from 35mm to 32mm.
the slp twins are 33mm the jaws D's are 38mm, and the stinger outlets are larger then the end of the pipe.
H
do you think 32.8mm is too tight on the d's?
I'm running cpc 48 with 540N mains and just looking for any input on combo. head are loose just above 60 on the squish on a 990
Not if you aren't getting det. and it still has good topend, I had my full
race setup down to 32s but felt like it had longer legs when I opened them up a little.
It also made it a little more forgiving changing alt.
I like to run pipes alittle tight with good fuel and plenty of it, the big bores
run better with a fair amount of piston wash.
Last edited:
7
clutching on the 975's?
sorry Scoop to hijack your thread
(Thanks Mike your input is priceless!)
now to my clutch set up (and not dialed in perfect yet)
cat 9 post pri 64 G cat weights
140/340 pri spring or 140-310
sec red/w in the middle
strait 53
20/46 last year and going to 20/45 this year hyvo
990 SW ported by turbotater
jaws Ds
cpc 48 mm with 40% 100ll
cpc twins
We talked about choking the twin pipes down for riding altitude. I have some big bore cpc twin pipes and the outet of each of these is 41.5 mm. My engine is a 975 and the pipes were for a 1150. How much choke should I start off with these pipes. And what r.p.m. should I shoot for?
We talked about choking the twin pipes down for riding altitude. I have some big bore cpc twin pipes and the outet of each of these is 41.5 mm. My engine is a 975 and the pipes were for a 1150. How much choke should I start off with these pipes. And what r.p.m. should I shoot for?
7
I would bring them down to about 33-35 mm ID IMO, we run the 990 about 33 for 6-9k there is a lot of guys who know and Dale Cutler is one, call cutlers and ask Dale himself. Even check with Mike Hobbs (hobbz?), or Wadye sp? (tubotater) these guys are priceless and don't post often so you might have to send a pm.
How ported out is the 975? are the carbs stock, bored, BB or after market?
How ported out is the 975? are the carbs stock, bored, BB or after market?
Similar threads
- Replies
- 0
- Views
- 903
K
- Replies
- 0
- Views
- 828
K
S
- Replies
- 1
- Views
- 403
S
B
- Replies
- 5
- Views
- 2K
B
- Replies
- 0
- Views
- 594