Bonneville America Forums Forums Technical Forums Performance Mods Jets or carbs or something confusing

Ok I have the CR II carbs So I the jet sizes are not the same as the stock carbs. But let me explain. I droped 40Ok I have the CR II carbs So I the jet sizes are not the same as the stock carbs. But let me explain. I dropped 4000 in elevation. I think the bike is running good except one thing. The idle is fine and bottom ¼ of the throttle is ok. Good response and everything!! But the top ¾ of the throttle is funny. If I give it lots of gas all at once it cuts out until I back off and then it back fires two or three times and then goes again. If I just hold it there it will eventually die. If I just “roll” into it and let the bike keep up it goes ok. Not good but ok. I am not sure what way to go with the jets?? Any ideas??

oh 1 more thing it is on 3 shims.. had it on 2 in Evanston ran good. Put it on like 6 or 7 here.. well it ran ok but the plugs was way black.

Normally, lower elevation requires a richer mixture. I bet if you clean the plugs, then check them after riding a while they will be sparkly white. You probably need to increase the jets a size or two.

when you figure it out let us know how much difference those carbs make, i agree with greybeard, and if you have the resources maybe check it on a dyno with a sniffer

Frank

i wish I had a Dyno. But I am a computer GEEK and I dont know anything about cars or bikes or anything. I just like to play around. Maybe if someone lives here buy me I can plan a weekend and go visit. I never drove the bike with stock carbs so I have no clue what the difference is. Maybe on the 21st I will have BigBill drive it. See what he thinks. I noticed that my order for jets went through last night so I hope to change them before the 21st. But I will let you guys know what he thinks the difference is.

They say for "Motercycle Racing Use ONLY" they must be better... right???

Seems like someone with those carbs has said you can't whack the throttle hard with them. I think you are off on your jetting a needle position, but by nature of design those cr's will dump too much gas if you just whack it hard.

Every bit as interesting as ValDean's carb problem, is where he lives in Arizona. That northwest corner of the state is "cut off" from the rest of the state. For him to travel anywhere else in Arizona, he must first leave the state, going into Nevada or Utah, then come back in at another point.

Check it out on a nice road map.....

Thanks for all the help and ideas. I am sure I will be posting more on this situation later. and he is right. I am "cut off" as my wife tells me when I get a little to much into the bottle. It is kinda funny I live in AZ but I work in Mesquite NV. so every day I dive over the border 2 times.

Hello this is ValDean (again). Here is what I have
2nd notch on the needles – 1600 feet above sea
Gas mileage ???
50 – 58 – 110 Mix screws set at 1 turn = lots and lots of popping.
50 – 58 – 110 Mix screws set at 2.5 turns popping is gone but top speed with just me (220) is about 90mph not a lot of pull
50 – 58 - 110 Mix screws at about 4.5 turns. More power and top speed is 95mph
Here is what I had before
3rd notch on the needles – 6000 feet above sea
50 – 58 – 115 Mix screws set at 2.5 pulls great
Top speed is 105 or 110 – with wife
Bad gas mileage I think so moved
2nd notch on the needles – 6000 feet above sea
120 miles per tank – without reserve
50 – 58 – 115 Mix screws set at 2.5 turns pulls good
Top speed is 95 or 100 – with wife

Moved again
50 – 58 – 115 pulls ok you need to play with the gass on the top ¾ 1500 feet above sea
Mix screws at 2.5
Top speed is 90

Right now
10 – 58 – 110 pulls ok. You don’t need to play with it -1500 feet above sea
Mix screws set at 2.5
Top speed is 90

Tried the air screws at 1 turn pops all the time 0 – 90
2.5 all popping is gone


When I get this working what should I be expecting?
Am I the only one with these carbs?


I forgot to tell you that the more I turn the air screws out the less response I have and the less pull I have and the less movement of the carbs and the less “sucking” of the carbs.

Just trying to give you the most information I can

Any ideas how to get it back to 115mph or 120 mph It should run better being lower in elevation but I cant figure it out.

Oh and buy the way I just ordered

100/90-18 AM41 Venom - 32psi $109
170/80-15 AM42 Vemon - 36psi $159
Plus balance and tubes not sure how much the total was but about $320 They will install them monday


Any ideas on the jets and stuff... Now remember I have the CR II carbs