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Exhaust leak can cause that problem as well as floats out of whack and the boot leak. exhaust leak should be easy to find and fix, boot leak - spray wd40 or starter fluid at the boot if idle changes, you have a leak. Float level you have to pull the carb and check, but if it is too low it will starve the carb for fuel and give too much air = lean.
Thanks, I will have to pull the carbs on Wednesday I think and I will set float height and double check some things. Other stuff I should go through while the carbs are off? I probably should sync them too but I haven't a caliper. I'll pick one up.
Way to show up HD! You thought I was just sitting around commenting on other people's posts! No way man I got two bikes now hahah! Neither running.
"lol" at the neither running. That's what I was like with snowmobiles a few years back. I've had a lot of vintage sleds, all projects, but when it's time to ride .. seems like there is nothing ever "trail worthy" when I need it the most. Always had one Arctic Cat ready though.
Projects are definitely fun, it's totally worth it in the end when you see your end result and all the time paying off.
I'm hoping so man. I'm having a wrench party at my place on Sunday so many of the DFW Texas cafe guys will be offering advice. Can't wait to look back over my shoulder at these obstacles! I'm interested in the project sled idea... When I get to WA, maybe I'll trade a bike for one and put it in the 'Specials' category on DTT as an avant-garde build... Hah!
I pulled carbs on the CB (very easy now) and cut the boots back, set float height to 14.6mm roughly, bench synced carbs, and put 130 mains in. Mixture screws out 3.5 turns and idle screw set to absolute lowest setting (counterclockwise). Apply choke, jump the shitty relay with a driver, and boom-
running bike.
The idle was a bit slow, and twisting the throttle left a hanging increase in revs. Things sound marvelous in comparison to the last idle. 1/3 were running a bit cold and 2/4 were hotter. I did not get to check for vacuum leaks before it got too late to run the bike. Damn HOA.
I am confident that it is rideable, but I am waiting for some carb pros to stop by this Sunday and offer advice. Some useless pictures below.
Now I'm really curious about the intake air side of those carbs. I haven't seen that type filter setup before. Any better pics and or details would be appreciated. From just the pic, I'm curious if those are the stock carbs.
Great work so far man, I have 4 gauge vacuum synch tool if you and your carb crew need to get a hold of one for your tuning extravaganza. Just throwing it out there, I'm just north of White Rock Lake
In the early pics you may see a shot of these GSXR carbs when I bought them. They are not stock CB750 carbs. The carbs are set up for dynojet stage 3 and the current settings are above. What photos/info would you like to see?
Coyote-
We have a couple guys bringing their carb tools. You should join the Facebook group! It's mostly forum guys, they have weekly bike nights at Dallas and FTW bars and stuff, I have driven to a few like a nerd. Good times.
Right? The brass is sweet and I love my dangling fuel filter. Can't spell brat without rat. I think the brass petcock is an underappreciated and very simple fix.
If you're off Sunday, try to ride over. Most of the regulars should be there from 12-8 and I'm buying food/drinks. If not, expect pics because it will be a cool event.
Good turnout from the local DTT crew at my garage. I bought a hell of a lot of hotdogs, but they all came for the motorcycles and Dr. Pepper.
At the end of it, I solved a lot of small problems that may have obscured my carb tuning. The carbs are officially synced and idle is set. Some of my most distasteful wiring and soldering was cleaned up and all problems with the starter have been abolished. Fuel lines have been re-run more conveniently, and multiple carb pulls to adjust slide needle/ main jets have ensured there are no vacuum leaks.
But unfortunately, the bike would die in first as clutch was disengaged. It seems that the main fuel circuit is not ready to handle any load. With the air filters removed, very sporadic backward sprays of fuel shoot from the under the slides. We went from 130 to 126 mains and a slide needle adjustment, but it just has no balls out of idle.
Tank sealed with redkote, fuel delivery system unobstructed, 126 mains and mixture screws at 2.5 out. Float height double checked and needles are clean too. Idle had backfires and died when revved. Sure wish I knew what the hell I'm looking for! On a guitar I can hear where the note should be and tune up or down to it. Here, I don't know what I'm listening for OR how to change it to where it needs to be.
Its difficult to say as there are quite a few variations of the Mikuni bst's with different jetting specs. I would be looking to go to around 115 with the main jet. I also had to enlarge the pilot air jet. What size are the pilot jets?
You say the Mikuni's had a Dynojet kit installed. You do know that the jet sizes stamped on Dynojet jets are different from Mikuni jet sizes?
Those squirts of fuel under the slides are the power jet circuit, on some BSTs they are blocked off.
Choke is being used healthily to start the bike, but it idles fine without it.
The bike is popping while idling but at the same settings (slightly richer on screws) it was just running fine, but dying with load. I cleaned all rust and double triple checked float height and needles, meticulously adjusting the float needle to make sure it fully actuated. No trash, no clogged floats.
The slide needles are set at second slot down out of 6 slots. Like I said, 126 mains in right now, close to the 122.5 stock. 4-1 exhaust and individual filters pushed me to 126, where it is still appearing to be too lean. I just read 20 pages of CB1100f and I plan to go home and take mix screws from 2 turns back to 3.5 turns out. I'll try to ride it around the neighborhood if that seems to work.
Should I be reading the plugs? I haven't once checked them since I installed new ones.
I don't know pilot jet/air jet size but I know that these supposedly had a Dynojet stage 3 kit installed prior. The idle is strong though... Should i be worried about pilot system?
Also, I did not let the bike warm up fully last time because the loud backfires pissed me the fuck off instantly and I killed it after 30 seconds to go find herbal solace.
Shoulda let it warm up before complaining probably.
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