1200 into a 1000 chopped

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Putzing away here. Yesterday I jetted up to 140 (#54 microbit) on the secondary main jet, up from stock 120, and 70 (#70 microbit) on the primary main jet, up from stock of 62. It frickin ripped the skins off the back tire. Had to be careful in corner take offs, but it bogged a bit at cruise, so today I did the same to the air jets. Odd thing about the air jets from Randakk, the 60 air jet mixes with the 120 secondary main jet and the 120 air jet mixes with the 62 primary main jet, chapter 9 of shop manual shows it nicely, but the jet sizes aren't labeled in the picture.
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I haven't run it for any time, but preliminary run was promising, better take off, like Joe says with his, the throttle is just instant, almost too much. No backfiring. Last night I had a lot of wild backfires at cruise speed, neither accelerating or decelerating. Plugs might be a tad lean yet, but I'm going to run it more before any more changes.

I cannot find much help with jetting of these style Keihins. I wish I knew what I was doing, but I'm having fun anyways. Second gear comes pretty quick. When the wife is along, I've started taking off in second. If only the stock gl1000 had come with a six speed.
 
good im glad your playing with the jets .....hows it feel to be the only two standing with this mod lately ....im thinking jetting might be last phase for me with the new carb rack im going to used ..the 75 rack rock gave me ...they are final piece and hooch will wear them ...

keep it up frankenjet :builder: :hihihi:
 
Steve said he jetted to 145. I'm not sure if anything else. I went 140 to start, but no other guidance to be found I decided to up the 62 jet too, because I felt mine had little dead zone between the two. I could have used washers, but decided to give this a go. I have some left over jets if it doesn't pan out. To me, what the heck do I know, it seemed to make sense to bump the air jets too as they feed the same jets. Hope to get some trip time in soon to see where the mileage might be. I'm busy trying to redo a bathroom here too. I'd rather be wrenching, and riding. I posted this to give you something to go by. Maybe others will opine. If you calculate the 62 x 1200/1000 you would want a 74 jet and the 120 x 1200/1000 would call for a 144. I went conservative.
 
Looking for advice. I believe, despite knowing next to nothing, that these carbs are different than most in that they have primary main jets and secondary main jets along with air jets. There is quite a bit out there for dummies like me on different keihin carbs, but none like the early Goldwings that I can find. I should haunt a few cb750 sites. Anyways, I bumped both of my jets up and after a bit more seat time, it is unbelievably quick off idle. Maybe 70 was too much for the primary main jet. Anyone else mess with jets with two mains before? The GL1000 manual says the 1/4 to 1/2 throttle is mostly controlled by the primary main jet, before the needle rises. I have to be very gentle in first gear or it launches me. I did another quick take off from a light last night and it leaves rubber and the back end goes to the left. It's kind of cool as I have never had a bike that would do that on pavement. At the same time it commands my respect. One these days, when one of us gets it dialed in, it will have to see a dyno. I am curious if there are hp and torque gains. I have never ridden a 1200 so all of my butt dyno comparison is with the 1000 and 1100. I am going to try and get my Magna tach on there as my Hercolor tach is all over the place, 3000 when it's 1000, 1000 when it's 4 or 5000. I should have gotten a Hiscolor.
 
ok I gathered from your previous post steve must have been posting again and took a look at his thread .....im glad he still at it ....you two guys have probably have closer motors to each other with the 20 plus thousand head shaving .....no I don't have any jet sizing info or time in this area at all ...on my motor its seems ive gotten all racks to work ....1000 1100 and 1200 racks but along the way there were other issues going on to compromise comparison ....it was all close though ....ive got a 1200 dresser running now that has 1200 carbs and early 1000 heads and cams ...its every bit as bad as hooch was at this stage....now that the timing thing is a thing of the past ...carb set up was simply spot on ....I think but cant know how different the compression between our motors is and how it effects this ....I cant think of having more power on bottom sheesh not where I live ..maybe on top hmmm I don't know it rather wicked up there ...I think on early rack 1000 maybe at where the needle starts working is the only slight spot .....and I might do the needle thing as my first move ...to be honest its almost a what for deal too
 
Cruised a bit with the wife last night. I take off in second gear with her on back because it's too jerky and tricky to stay smooth. I have to get a decent seat and back rest for her. I also synchronized yesterday. It will run smooth as silk in fifth gear from 25 mph up. No lugging sounds. I am surprised that with the 1000 heads and cams that it has no spark knock sounds like my 77 does when taking off.
 
yeah for high rpm cams its sure.adds low end torque ...just gose to show you what bs is out there is just blab to hear the jaws flap ....hooch has so much more torque at low rpm than a stock 1200 its just rediclues to think the stock cams came close to making more low end torque what a faislure of engineering on hondas part ....im getting no noise and nothing but torque from 1500 rpm in fifth gear even on the hills around me ...simply amazing to me
 
I took mine for a couple hundred miles yesterday. I was getting just shy of 40 mpg. It started running rough and backfiring again. It would come and go. Seemed like if I opened her up for a bit it would clear itself and run good for a while. I'm probably too rich with the two jet changes. I may have gotten some bad gas as it ran better after I filled up. I also started pushing antifreeze out the puke tank a little. I'm going to pull the carbs and check under the screens today, then probably put the stock 0.62 primary jet back in along with a stock 70 air jet and see what that does. My plugs were tan, but something's wrong as it is a bit boggy in upper rpm.
 
hmmmm if im having trouble anywhere it is at high rpm where the cam is suppose to be its best but it slight if any at all I keep thinking it so great overall that the huge burst commonly associated with these cams is eliminated by the new attitude of huge torque from idle on ...hard to say with mine ...200 mile run ...I need one ...got to get shield first ...
 
I put the 62 jets back in today and it made it less jerky, but I miss the instant rev it had. Still spins the tire taking off, but better in the upper ranges of rpm. I may try the 120 main again with a 70 primary or if I can get them, a 130 main and around a 65 primary. The off idle instant rev was amazing compared to this and the other bikes, 1000 and 1100.
 
I am getting really good at taking carbs off. After about ten more tries including a set of 1200's, I think I'm happy with my 77 carbs with a 140 main, 70 air and a 65 primary and 120 air jet. I don't think the 1200's are a good deal for this setup because of the sudden transition of the intake charge coming down the elbows of the 1200 which are much, much smaller than the 1000 elbows. But when the charge from the 1200 gets to the head, it drops into a non-matching port which is larger and not centered on the 1200 elbows. They will bolt up, but it seems to be a downgrade in performance. I'm thinking the flow is messed up right at hat junction. Maybe they could be ported to use the faster charge, but that's beyond my caveman skill set. I took mine for a cruise tonight and it pulls awesome from start to 9 k. When I win the lottery, I'll order a c5 kit to see what that can do, but I'm really happy with it now. Hope to get some real paint on it this winter.
 
If mine is dry in the morning, I may put my pump back on. Tonight it didn't feel like it was running out of gas though. I just drove it in the city tonight. Yours will like the 125.
 
I went for a ride yesterday in the 92' heat to cool off and finally get some miles in. Didn't get far. It started to back fire, loudly and miss. Then it started to die if I got on it. Frustrated, I limped home. Today I checked wires, homed coils. Decide to replace #3 wire and plug. I think it may have been the plug. I took it for a little jaunt and it was much better. Got on it hard a few times. Seemed to be missing a little, but hit 5 k and took off. I hope this isn't heat related. It's supposed to warm to the 90's again by the weekend. We shall see.
 
hmmm seems the problem I was having sounds different ...eric on my bike the slides are banging all the open in no where close to full throttle from the extra vacume and flow provided by the extra 50 cc per cylinder

in no way are the slides matched up to this ... changing jets just changes where the problem will be at ....unless you put in stronger springs in slide or weigh them down so vacume cant slamed them home your not going anywhere in fixing this .....personally this problem was all needed to dump the stock racks and going with single carb set up ... where the vacume plays no part between carb and motor
 
I am still running lean I think based on plug color when holding higher rpm. Might be a bit rich on the bottom end. Guess and check, I hate guess and check, but I cant afford a dynometer and associated equipment, so....guess and check. Im going to try another washer under the needle or else go up to 150 on the main.
 
Separate post, but connected. I have four sets of 764a carbs, but two sets have tall springs and two sets have short springs. I wonder which length yours have, Joe.
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I am currently using the taller springs. Tonight, I will compare the slide weights to see if there was a reason for this. They each have the same number of coils.
 
mine are tall eric sheesh ..ive never seen short ones like that ... and yes im thinking by the time gas is is getting right at rpm bowls are running out of gas also ..so don't think to much on plug color ...swing are way to great for fuel to be consistent as In lean and rich
 

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