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Here are my results from a dyno by Ten Swafford of the Legion of Zoom.[luv the title of his company]. He was recommended by Sweatmachine[thanks Jeff] and is very knowledgeable about tuning. Now before you freak out over the A/F understand the reason for this dyno was to give me the numbers I need in order to fine tune the carbs since I just finished an extensive cam change and a port and polish. The first page run was at 4th gear and by the squiggley lines, that is where the bike takes a "dump" before getting the gas required to go. The second and third page is at 3rd gear and she dumps at 4,000rpms. I have a 19t front sprocket just for added insight. We changed the clip setting and she did respond a little but I left a few horses on the table do to SEVERE leanness. After I change main jet, main air jet, slow jet[for better idle] and jet needle size, I'll be doing another series for comparison. I'm pretty pleased with the HP that the street cams and CR-S carbs have delivered. I'm running 115 mains and 60 pilots and plan to buy 135,140 and 145 on the main jet. I hope to crack 70 hp or at least get REAL close.






 

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SHRuuM those are some good numbers for a stock motor.You might want to check for vac leaks that thing is running to good for those fuel readings or ether that guys fuel meter is not right.Mine looked like that once and the rubber on the intake/carbs where leaking.
 

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SHRuuM those are some good numbers for a stock motor.You might want to check for vac leaks that thing is running to good for those fuel readings or ether that guys fuel meter is not right.Mine looked like that once and the rubber on the intake/carbs where leaking.
No we checked for leaks by spraying around the carbs and manifolds and everything was tight. The guy is quite professional and thorough. My numbers before the cams and head work were 13.5 to 14. And the fuel meter is calibrated before the run. I was asking a lot of questions and he had the patience to answer them all as well as give me sound advice. We did an adjustment on the air needles as that too were waaay lean. Here is partial pic of his rig.

 

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"I'm pretty pleased with the HP that the street cams and CR-S carbs have delivered. I'm running 125 mains and 60 pilots and plan to buy 135,140 and 145 on the main jet. I hope to crack 70 hp or at least get REAL close."

SHRuuM,

From where you're at HP wise, 70 hp looks well within reach. Which cams did you end up running?

I have a set of CR carbs I scored off ebay just sitting on the shelf waiting for installation and, from all the posts I've found relating to jetting, you're going much bigger than most on the main....is this due to the head porting/cam or have you also gone bigger on the valves?

BTW, 70 RWHP is also my goal on my Thruxton...

Cheers,

--Rich
 

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Discussion Starter #6
"I'm pretty pleased with the HP that the street cams and CR-S carbs have delivered. I'm running 125 mains and 60 pilots and plan to buy 135,140 and 145 on the main jet. I hope to crack 70 hp or at least get REAL close."

SHRuuM,

From where you're at HP wise, 70 hp looks well within reach. Which cams did you end up running?

I have a set of CR carbs I scored off ebay just sitting on the shelf waiting for installation and, from all the posts I've found relating to jetting, you're going much bigger than most on the main....is this due to the head porting/cam or have you also gone bigger on the valves?



BTW, 70 RWHP is also my goal on my Thruxton...

Cheers,

--Rich

I have a set of CR carbs I scored off ebay just sitting on the shelf waiting for installation and, from all the posts I've found relating to jetting, you're going much bigger than most on the main....is this due to the head porting/cam or have you also gone bigger on the valves?



I scored the street cams from British Customs. You can't use bigger valves unless you get the big bore kit do to clearance. The port and polish is probably one reason for bigger jets but I really think its the cams since I was on target before the install. I didn't want anything radical, cam wise, since I commute daily and need reliability, but still wanting to get horsepower without the big bore kit. I'm at 90' above sea level so my results will be different than higher elevation. I talked to Chad at Sudco[the guru of the Cr-S carbs] and he suggested to start[in my case] 135 mains, 65 pilot and 5180 on the needle and adjust from there after another run. He stressed to start with small increments so I'm not shooting all over the place. This way I'll know which way to go in order to completely dial her in and get the most bang for my buck.
 

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I cant see how the cams would lean it out that lean,thats way way lean.125 sounds small with good pipes and no air box even for stock carbs.One thing everyone need to know when dealing with any mechanical slide carb ,forget about the niddle till you get the main right,its not in play on these carbs as it is with stock vac. operated slide carbs.Once you open the throttle wot the niddle is not in the hole at all.If that fuel reading is right i bet that bike will pick up power on a wide open roll off to 7/8 throttle.From what it showing its so lean its cooking your motor.Any thing over 15to1 is danger zone.My guess would be a 140 to 150 main going by that chart.
 

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I cant see how the cams would lean it out that leanMy guess would be a 140 to 150 main going by that chart.

The cam lobes are ground down on the lower side and extra metal added to the top, tip for a bit longer duration. During this part the motor is asking for more mix but the carbs are out of fuel so the only thing left during the intake stroke is air...thereby making it lean and starving for fuel. She's parked and won't run til after the jets arrive and I'll be sticking by what Chad at Sudco recommended, since he is the guru of the CR-S carbs and start with 135's[but ordered 140 and 145's], a 65 pilot since idling is a problem and a 5180 needle which is the next size from my 5181. This is all by the book and recommendations to start with and work my way up progressively till I reach the desired A/F.
 

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The cam lobes are ground down on the lower side and extra metal added to the top, tip for a bit longer duration. During this part the motor is asking for more mix but the carbs are out of fuel so the only thing left during the intake stroke is air...thereby making it lean and starving for fuel. She's parked and won't run til after the jets arrive and I'll be sticking by what Chad at Sudco recommended, since he is the guru of the CR-S carbs and start with 135's[but ordered 140 and 145's], a 65 pilot since idling is a problem and a 5180 needle which is the next size from my 5181. This is all by the book and recommendations to start with and work my way up progressively till I reach the desired A/F.
the only thing more cam does is make less vac at lower rpms and flow more all the way through,yours is lean all the way through and its not just a little lean its way lean.Just a little change wont cure yours as lean as it is.Even with stock carbs and preds no air box you need atlest a 140 main on these bikes.If the cr carbs flow better then stock carbs you might need more then that(if the jets are the same size pre number as the stock carbs)maybe the guy knows something I dont ,I dont know anything about cr carbs,I cant see running them they dont flow enough.Did you get any spec. on the street cam lift /duration?
 
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