justinvintageyamy
New member
What am I missing??? replaced the butterfly carbs with 38mm roundslides. I just noticed that my 1980 SRX was only running 8000 rpm. I looked to see if the slides were going all the way up and they weren't. It appears that if I raise them, then the idle is too high. please help. thanks.
tedgoesfast
New member
you obviously changed throttle cable did you change the thumb lever
justinvintageyamy
New member
yeah, I bought this from a guy that had put these carbs on. The old throttle cables didn't come with the sled, but I didn't think they would work with the roundslides anyway? The thumb lever is stock. thinking about modifying the thumb lever...
tedgoesfast
New member
if the thumb lever is stock it does not have enough throw to pull carbs all the way open i dont know what would work
justinvintageyamy
New member
I'm sure I'm not the first one to do this.....someone will have an answer I'm sure. Thanks.
tedgoesfast
New member
if they dont work ive got sets of flatslides off of 600 v maxes i parted out 3 of them
YAMMIEGOD3:16
Active member
CORRECT, VERY GOOD TEDGOESFAST. SOME USE TO NOTCH OUT THUMP LEVER FOR MORE PULL. BE CAREFUL WITH THIS. SLED WILL THINK IT HAS A STUCK THROTTLE. 3:16 (yammie tony)
justinvintageyamy
New member
do flatslides require less throw??? How would these solve my prob? thanks. what size flatslides? What do you mean that the sled will think it has a stuck throttle? What do most people do that go to roundslides, there has to be a simple solution...
tedgoesfast
New member
yes flidsides are on a rack less throw but iam not sure if the distance they are set apart is what you would need
GP292Racer
New member
If the lever is plastic, just heat it up and bend it out a bit. Gives you more throw, I did that for the last set of 38's, worked fine.
justinvintageyamy
New member
It's metal. It can't be too hard to modify. Any other ideas anyone??
opsled
Active member
You need a throttle block assembly off of a 78 or 79 SRX.
The distance between the thumb lever pivot and where the cables attach is different depending on the carbs the block is designed to open. Butterflies and racked carbs will be different than unracked round and flatslides as they use levers on the carbs to open them so the movement needed buy the thumb lever can vary depending on the lever arrangement on each carb setup. Unracked round and flatslides need to have the thumb lever pull the slide to the top so they will usually need a longer arc in their movement to get the job done. The larger the diameter of the carb the more movement is needed. 44mm carbs need more arc in the thumb lever than 38's, 38's more than 34's etc. The difference in length between the throttle cable and it's outer sheath is also different depending on the size of the carb so cables for 38mm carbs don't work for 44's.
You can try to modify your stock 80 throttle block and you may have some success but the right way to do it is to use one that was designed to work with the carbs you have.
I don't have a stock 80 throttle block to measure but do have one off a 78 SRX (which had roundslides). It measures 2 1/2" from the center of the pivot bolt to the center of the cable hole. As an example to compair I measured one off an SRV (which has a butterfly carb), it measures 1 7/8" at the same points. That difference is where your problem is.
Good Luck, opsled
The distance between the thumb lever pivot and where the cables attach is different depending on the carbs the block is designed to open. Butterflies and racked carbs will be different than unracked round and flatslides as they use levers on the carbs to open them so the movement needed buy the thumb lever can vary depending on the lever arrangement on each carb setup. Unracked round and flatslides need to have the thumb lever pull the slide to the top so they will usually need a longer arc in their movement to get the job done. The larger the diameter of the carb the more movement is needed. 44mm carbs need more arc in the thumb lever than 38's, 38's more than 34's etc. The difference in length between the throttle cable and it's outer sheath is also different depending on the size of the carb so cables for 38mm carbs don't work for 44's.
You can try to modify your stock 80 throttle block and you may have some success but the right way to do it is to use one that was designed to work with the carbs you have.
I don't have a stock 80 throttle block to measure but do have one off a 78 SRX (which had roundslides). It measures 2 1/2" from the center of the pivot bolt to the center of the cable hole. As an example to compair I measured one off an SRV (which has a butterfly carb), it measures 1 7/8" at the same points. That difference is where your problem is.
Good Luck, opsled
snopro
New member
buy a new throttle block from Wahl bros or Cat. problem solved.
justinvintageyamy
New member
do you have a part number? don't want to order the wrong one. thanks.
opsled
Active member
I put a slide Keihin off a '77 on my '78 Exciter to try and had to change the thumb lever also to get it to open all the way. I could only get about 6200 rpm's with the '78 thumb lever on there. Now I'm getting about 7400. although I'd like about 8500. he he.