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Re: 1973 CB350... my first bike build (need carb help!!!)
charged the battery over night. started right up on both cylinders, running on both cylinders from the start and she sat there idling perfect at just over 1k rpm.
i turned up the idle a hair and let it run for a few minutes before shutting it down and eating dinner.
i was so fired up that it seemed to be running well, that i put the chain back on and decided to take it for a ride even though it was freezing cold.
thing ran like crap. hardly any power and it was screaming when i came to a stop instead of dropping down to the nice idle speed i had set it at earlier.
now it was doing this one other time before it blew up and a guy synched the carbs up and it ran great.
so how do i go about synching these things? no vacuum ports for those not familiar with the 350s
Re: 1973 CB350... my first bike build (need carb help!!!)
A failure to return to idle usually indicates a rich condition. Also, if the bike starts and runs well, but gets worse as the engine heats up, this will mean it's running rich as well. If it's especially cold, your bike will run a bit richer, but usually not that bad.
To get the carbs into sync, first warm up the bike.
After that, pull the plug on one side and adjust the idle screw until the bike will run on one cylinder. For the cylinder that's running, adjust the air screw in or out until the bike is at max RPM. Repeat the process for the other cylinder. Now make sure the bike is running for both cylinders and dial down the idle to 1200 RPM.
Re: 1973 CB350... my first bike build (need carb help!!!)
^^ good stuff man, thank ya!!
i did exactly that and she's running a hundred times better. dropping back down to idle quick after coming to a stop and she will sit there ALL DAY idling smooth as can be at 1,200 rpm. i pulled the plugs and checked them though and the right is still rich and the left lean though.
couple pics in the driveway just for fun
gaaah
i was ready to buy a set of Mikunis from DCC but apparently they're out of stock and don't know when to expect any because of the whole earthquake/tsunami thing. i just can't get these things sorted for the life of me.
i did get a new chain in the mail today so i'm going to throw it on this weekend
i took a break from the bike since i was just so frustrated with not being able to get it running right. last week i bought some new jets from DCC (stock sizes, 68 and 105) since the o-rings on mine weren't in great shape. this seems to have helped. bike is idling nicely, pulling hard (only running it up to 5k rpm... still breaking it in since the rebuild. need to change the oil soon), returning to idle quickly, no backfiring, popping, sputtering. it takes gas well when hitting the throttle from idle, but isn't as responsive as i think it could be... maybe i'm asking too much though. i dunno.
i pulled the plugs and it is running lean though. where should i start for jet sizes? still running stock filter and aftermarket mufflers (although they look very similar to stock and are very quiet
i installed a new chain this afternoon too.
I was going through your build thread backwards, saw the seat and saw a local shop did it. I though, "Man, I wish there was a good upholstery shop around here..." Then, I went back a few more pages and saw you are in Pittsburgh too!
as i posted a while ago my bike seemed to have the same problems but i was running rich. i came down to (if i remember correctly) to a 70 and 110. I may have went even farther to the stock 68 because idle where was i was having issue but i surely went with the 110. i just ordered each jet from DCC in 3 sizes and went from there. does suck pulling them just to change the jets that much but beats changing your plugs every other week. bike looks great, ive really been missing the old school flare that i stripped off the bike lately. my next build wont be so bare. keep it up
the guy who did my seat is Jerry Berberich... he's located in Overbrook, a couple blocks off of Route 51. i'm pretty sure this is his number 412-885-1585
he works right out of his house so his wife may answer the phone haha
that was just putting around town. still taking it easy since i only have a few rides on it since the rebuild.
the very last photo made it look alot lighter than that left cylinder was. the picture before it is more indicative of the coloring for that plug.
do i need to go up on both jets? like i said, i'm at 68 and 105 now... what do you recommend trying? the bike is running good with no popping so i don't think i'm far off
Ride the bike and put a few hundred miles on it and then look at the plugs again. These CB350s are not like modern day sportbikes that have engines design to run at peak performance and need exact jetting. The CB350 can run with no air filters, velocity stacks, pod filiters and open exhaust or megaphones....doesnt matter.......with stock jetting and be fine. The only time you need to be looking at rejettting a CB350 is if you have done major engine perfomace changes for a race motor(race cams, modified intakes, etc)......a motor that is gonna be run at redline for extended durations. With the setup on your bike, use the stock jetting specs.
Did you check the little black rubber plug that covers the slow jet? If it is hard and not soft rubber like the o-rings on the jets......it needs to be replaced.
Also.....the important thing with a fresh motor is to make sure you heat cycle it several times, allowing the motor to come up to normal operating temp and then turning it off to cool down. This allows the new internal parts to seat themselves into position. After a handful of heat cycles the bike should be okay to run like normal. One thing I always do with a new motor is, recheck the torque of the 8 head bolts on the top of the engine. They always need to be re-torqued.
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