|
|
|
|
Hello all,
I have just finished rebuilding my carbs for the first time. All seems to be well, other than a high idling RPMs after rolling on the throttle. I have adjusted the throttle screw under the carbs, and the bike idles properly (or close, around 1000-1200 RPM) when the bike is first started. However, as soon as the RPMs exceed 4000 or so, they do not decrease, even with the throttle completely closed. I've checked the throttle cable and choke, and each of those seems to be working properly. The choke is not stuck open.
The bikes RPMs are fine when riding in gear once the clutch is completely released, but as soon as the clutch is engaged or it is shifted into neutral, the RPMs return to about 4000.
My initial thought was that the choke was stuck open, but that does not seem to be the case. I've had the bike for about a month, and I only have about 3 weeks of experience working on it. I may be missing something entirely obvious. My guess now is that something is sticking and not returning to its normal position, but I don't know where to start looking. I may have even caused something myself when rebuilding the carbs. Also, I have not synchronized the carbs since the rebuild (sync tool is in the mail), would this affect the idling speed like this?
Any advice or ideas would be much appreciated! Thanks!
"Adventure is just bad planning" - Roald Amundsen
1979 Honda CB 750K
|
|
|
You need to see if the vacuum diaphrams have any tears or holes in them.
On a Roadstar Adventure.
|
|
|
Definately if the carbs aren't in sync you will have some rough idling problems, but definately check for vacuum leaks first since that is easier to diagnos. Have you gone to your local bike shop to price out how much it would cost just to have the carbs synced? Would save you some time at least.
I know you also have to adjust the idle when the bike is totally warmed up otherwise your bike will jump up in rpms, I have an 81 that did this to me and all we had to do was finese with the idle screw everytime it would jump up in rpms while it warmed up until it was all warmed up and settled out, then problem was gone.
|
|
Administrator
|
When I did the carbs in my v45, I had a really high idle. Turns out you need to "bench sync" the flaps on the carbs. Idle speed is controlled by the flaps that used to be choke plates on older carbs.
I used the wire from a honda carb cleaning tool for the 40 sized jets. I then set the opening of each flap to just allow that wire to slide in and out, kinda like a feeler gauge and valves. Once all 4 were set to that, my idle issue cleared right up.
The ride IS the adventure. The destination is just to get gas!
|
|
|
Thanks everybody for the ideas and advice, now I'll have some direction for my troubleshooting. Much appreciated!
"Adventure is just bad planning" - Roald Amundsen
1979 Honda CB 750K
|
|
|
You may have an air leak between the air box & the carbs. Check by blowing propane gas in this area whilst bike is running. If revs increase more you have a leak.
1980 CB750F S/S
1979 CB750F
York
England
|
|
Administrator
|
Uhmmm...not so sure propane gas is the best thing. Carb cleaner might be a better alternative.
I just have this vision of a stream of fire making its way back to the propane tank, and something going boom.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
|
|
|
Well, a propane blowtorch is supposed to be lit. If you were using one of those (unlit) then I can't imagine any issues.
That said, carb cleaner, starter spray (not too much) or even wd-40 would also work and is probably easier to use.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.
|
|
|
I have used propane before (unlit) to check for vacuum leaks, but pretty much anything that is a flamable gas will work, even like a can of axe body spray should work great, I know they make great flamethrowers for killing bugs!
|
|
Administrator
|
 axe body spr....dude,you're a piece of work 
|
|
Administrator
|
Which reminds me of a joke.
What is the most common epitaph (tombstone writing) in West Virginia?
"Hold my beer, and watch this!"
No offense, Hellbilly.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
|
|
|
oh come on, like you guys never tried it before, I don't even buy that spray anymore to put on, I mostly use it for flamethrowers, lol, u will never have to work so hard on trying to get those fast moving or hard to reach bugs again!
thanks Luke, I think I now know what I want on my gravestone when I die
|
|
|
It's cheap to! One dollar at the local Dollar Store!
American by birth. Cowboy by choice!
Vero Beach, FL
http://i373.photobucket.com/albums/oo172/grandpaslinger/HD%20Road%20Glide/IMAG0046.jpg
|
|
|
Ha! See I'm not the only redneck on this forum, lol! And it also smells better than propane, even when lit 
|
|
Administrator
|
Oh I've done it! But not with perfume. Go big and use a can of Raid wasp and hornet killer. It has a 25 foot spray  You get some serious long distance flamage with that stuff  Plus,it's real thick and when it hits the ground it burn for several seconds. Almost like OTC napalm!lol
All this talk about arsen made me think of this pic.
|
|
|
Nice nice, it just so happens I picked a can of that up the other day to take care of a few bees nests... hmmm... bees smothered to death or burnt to ashes in a 25 foot flame.... lol, shouldn't give me ideas like this!
|
|
Administrator
|
Mine was doing the same thing, the adjuster under the carbs, 3 full turns in too much.
Let us know what you come up with guy.
|
|
Locked
