Cafe Racer Forum banner

1 - 20 of 24 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
i just got my cb450 running pretty good (basket case when i got it). i rebuilt the carbs with K&L kits, set the floats at 14mm, set the IMS at 1.5 turns out, installed new throttle cables, new clutch cable, cleaned and gapped plugs, made and installed new intake gaskets (rubber boots look good, new battery, disassembled the automatic timiing advance, cleaned it, lubed it and put it back together (might need to springs) and i adjusted the valve clearences. what i havent done is set the ignition timing, adjust the points, put air filters on it(the old ones are shot), and it still has the same plugs, plug wires, and spark caps on it that were there when i bought it. now it starts right up (with the choke off). it runs smooth, and revs up fast, but it doesnt decelerate like i think it should. most of the time it will bring itself down to about 2500-3500 rpm. sometimes it will just hover for a second and come back down to 800-900rpm (using mech. tach.). i tried adjusting the idle mixture screws but the are unresponsive on both carbs. i also checked for vacuum leaks by spraying carb cleaner all over the boots and gaskets. it also has slim fuel filters on both fuel lines with see through Tygon fuel line, and i can see the line full of fuel. but on a good note the bike screams!! its just i dont want to overheat because of this high idle/deceleration thing.
 

·
Registered
Joined
·
2,595 Posts
Interesting. (I'm going to be going through the same procedure soon with mine.) I don't know diddly about those CV carbs, but my guess is either the carb slides are hanging up a little bit, or maybe the throttle cable routing is wrong. Does it make any difference if you move the handlebars back and forth when it's idling? That's a quick way to determine if the cable routing is ok.
That's all I've got.
Welcome.

FR
 

·
Registered
Joined
·
278 Posts
Man, it's nice to see someone lay the necessary groundwork before asking why the hell his bike won't run right.

First problem: the correct float height is 20mm. You've got too much fuel in your bowls.

Second problem: your bike's unresponsive to mixture screw adjustments - that's typically because the air passage behind the mixture screw is full of mung, though it might just be because your mixture is way too rich. Fix your floats, and if you can't make the bike rev or stumble with the mixture screws, pull your carbs and clean out that channel. If you stick that straw the carb cleaner comes with down into the hole behind the mixture screw and spray, it should pop out in two places - on the bottom of the carb (inside the bowl) and out the filter end of the venturi. If it's only coming out in one place, stick your finger over that and spray until it finds the second hole.

Glad you could join us buddy.

Edited by - xander450 on Aug 07 2007 9:13:43 PM
 

·
Registered
Joined
·
13,809 Posts
if that doesnt work, make sure the orings on the jets arent torn. one that leak with siphon fuel past and cause it to idle high. just somethin to think about and check later.

jc
 

·
Registered
Joined
·
9 Posts
Discussion Starter #5
my clymer manual states that the float height is supposed to be 14mm. it was set at about 25mm before and it ran like crap. if the float height was too high then wouldnt my carbs puke all over the place? i dont think the vacuum slides are hanging up on anything, they are very smooth through their movement. i was thinking the same thing about a busted oring or something. but i was looking at the pictures of the carbs in my book and its not showing any oring for the jets. and i dont think i have any orings on the jets inside of the carbs (except the IMS). keep these ideas coming! i NEED to ride this bike before i take of for kuwait. thanks for the help so far
 

·
Registered
Joined
·
278 Posts
Well, friend, that's odd.

The instructions:


...and the book it came from:


...and here's some forum references to the 20mm float height standard:
http://www.motorcyclekb.com/Uwe/For...orrect-way-to-measure-float-height-on-a-CB450
http://www.nonsolonews.net/thread-72-0-2575-17/rec-motorcycles-tech/Honda-CL450-fouled-plugs.htm

Man, I clearly have nothing to do tonight. Just set your floats to 20mm. And no, 6mm isn't really enough to make your carbs spill. It is, however, easily enough to throw your mixture and provoke high RPMs.

A
 

·
Registered
Joined
·
9 Posts
Discussion Starter #7
wow now i want to know what information is correct. i thought i was taking my information out of a clymer manual, but i was wrong. im using a Haynes. the book says its for 500 and 450 twins, 1965-1978. i just double checked this book and it does say 14mm from carb base. im still going to take these carbs off tomorrow and change the floats to 20mm from gasket surface.
 

·
Premium Member
Joined
·
10,737 Posts
lil teddy haynes became frank "big dick" clymers bitch years ago.

other than this observation, i got nothing for this thread.

texy

p.s.- both these manuals suck, try to find a honda factory manual!
 

·
Registered
Joined
·
1,731 Posts
I have to wonder if the 14mm from carb base vs 20mm from gasket surface are the same measurement with different starting points? See if the gasket surface to the edge of the carb is 6mm and then you'll know!

quote:lil teddy haynes became frank "big dick" clymers bitch years ago.
Tex - it's John Haynes and Floyd Clymer. Floyd died in 1970 and I think Haynes is still alive.

Jim
 

·
Registered
Joined
·
9 Posts
Discussion Starter #10
ok guys i tried what you said. i set the floats to 20 mm and started it up. i used the choke to start it (i dont know if i had to), and it started up really fast. it sounded about the same. accel fast, decel slow, idle smooth and sometimes hovered at higher rpms. the IMS still have no effect, but now i noticed a slow drip of fuel on the right side carb (dripping right off of the bottom). my next move is to cut one coil off of the spring for the auto advancer unit, and then im thinking about raising the float to 22mm because it still seems like its getting too much fuel. any suggestions?
 

·
Registered
Joined
·
687 Posts
did you pull the carbs and verify that the passages are clear? didn't see you mention it.

...connoisseur of slack...
 

·
Registered
Joined
·
9 Posts
Discussion Starter #12
ummm no... im throwing my hands in the air with this bike right now. im going to pull the carbs off and totally go through them..again. i HOPE there is something i missed.
 

·
Registered
Joined
·
1,731 Posts
Correct me if I'm wrong but aren't K&L carb kits made by Keyster?

Playinsafe44 - did you use the jets out of the K&L kit? If so, clean your OEM jets and put them back in. Same thing with the needle. The K&L/Keyster stuff is notoriously off from the correct spec. Make these changes then if you've still got too much fuel, raise the floats. The Keyster needle valves are the only decent part in the Keyster kits (besides the gaskets) but they tend to require a little extra float "height".

Jim
 

·
Registered
Joined
·
278 Posts
I wouldn't be too surprised, it's pretty easy to miss something in there and wind up having to pull the carbs again. Float height: I wouldn't if I were you - you'd be correcting throughout the range for a problem that only exists in one portion of the range. Besides which, that 2mm isn't going to correct your leakage problem, but do it anyway if you feel like proving it to yourself. Unless you're leaking from the bowl drain screw (unlikely), odds are you're seeping from the sides of the bowl or the overflow, meaning you have way the hell too much fuel in there. So much, in fact, that the only reasonable conclusion is that your float needle isn't properly seating. 2mm of float height adjustment won't change that.

Pull and clean your float needles and seats, make sure your floats aren't leaking (shake em next to your ears), and for the love of god blow out that passage behind the mixture screw. If your mixture screws don't work, your carbs don't work.

A
 

·
Registered
Joined
·
23,303 Posts
sounds to me like it is getting more air than fuel. If it were more fuel it would be a bog, more air makes the engine race and also surge on deceleration.

oh and put the hond metal parts back in your bike (clean of course). Those K&L kits are garbage. If I ever find the person who puts those together I am going to break his hands.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #16
well i took my carbs off and im attempting to clean them again. i took out ALL of the jets like i thought i had done before. the only one i wasnt too sure about was the one right next to the main? jet. its the first brass jet on the shorter of the two stacks. it has "38" written on it. im just making sure that this one doesnt have a hole going through the top of it like all other jets ive seen. there was one passage that MIGHT have been clogged. when you look at the intake side of the carb there is a small brass tube right underneath the choke butterfly. i had to spray carb cleaner in it for awhile before it actually went all the way through. there was a difference i noticed on the needles. the original one has the number "053000" and the replacement has "D14". all of the replacement jets and everything else look identical. i was also wondering how to do the timing. i have a timing light... i also want to make sure the cam chain is adjusted correctly, but not sure how. and last but not least i want to redo my valve clearences. i would really appreciate the help. thanks a lot
 

·
Registered
Joined
·
23,303 Posts
just because you don't see a difference doesn't mean there isn't one, unless you are mic-ing everything out to check for thousandths of an inch you are not going to notice a difference by eye. Your bike will however.

have you bench tested your vacuum carbs on the bench? There are a couple of ways of doing this but basically if you have a compressed air source you can either blow in to the moutn of the carb directly and work the butterfly to see how the slide reacts, or you can find the vacuum passage and put the compressed air hose nossel in there and see how the silde opens and closes.

I had a problem with DOHC cb750 carbs once of slides sticking where it turned out a very small nick was hanging up the slide in the bore. It was so small I could not feel it with my finger.
 

·
Registered
Joined
·
687 Posts
the instructions in your manual should be sufficient to set the timing without anyone here needing to write a dissertation. the only thing i might add to what it will tell you is that the point adjustments are tiny, a mm or two at a time. if you make huge movements you will throw the timing off even more.

...connoisseur of slack...
 

·
Registered
Joined
·
9 Posts
Discussion Starter #19
ok so i was ALMOST done rebuilding the carbs for the second time when i screwed up! i had finished the first one and i think i had found one passage that was still clogged. so i redipped both carbs, and shot carb cleaner through it all, and they were spotless. then i put in all the stock jets. i was about halfway done putting the second carb together when it came time to install the jets... the main jets went in fine. but when i went to put the top part of the slow jet in, it snapped in half! (im talking about the jet that has "38" written on the top and it doesnt have a hole through the top) it all came out of the carb body just fine. now my problem is that i dont know where to get this little unique jet. normally i would just buy a set of carbs off ebay, but i leave for kuwait in 2 weeks! does anyone know where i can get this part?!? anyone want to sell me one? HELP!
 

·
Registered
Joined
·
23,303 Posts
have you tried your honda dealer? I know they have individual carb parts for a lot of their older bikes. YOu may have to order it though. Also sudco should have it but you will ned to know the model of your carb as they don't do things by bike model anymore.
 
1 - 20 of 24 Posts
Top