RPM hang up ?

[Guest]

well on my 81 sh project i cleaned the carbs put them back on and sync them but it was hanging up 3k and slow to come down i was told could be a vac leak,carb linkage hang up on boot clamps or throttle cable check linkage and it snaps right back down so the cable and linkage are good now my boots were in real bad shape even found a couple of hair line cracks in side i now have new boots and rechecked carbs when off well i ran the bike down the road today for the 1st time runs smooth but is still hanging up at 3k and came down slow and when i crack the throttle up higher it stuck right at 4k had to shut the bike off, then starting it back up and it idled perfect what can it be??????

[catdna]

I have the exact same problem - and after a thorough inspection yesterday, can confirm that I have no air leaks.

However, I'm running 'pod' filters and a 4-1 exhaust (brand unknown) - but I found this page last night :

http://hondanighthawks.net/carb13.htm

- it states that ....

>>>
If the throttle is lightly “blipped” at idle, and the rpm “hangs up” before dropping to the set idle speed, and there are no intake leaks and the idle speed is set to less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm.
<<<

(lots of other good reading on there about carbs in general)

Now, I checked with a colourtune and try as I might, I couldn't get a 'yellow' flame at all (on any cylinder) indicating that the bikes running very lean (understandable I guess given the filters / exhaust).

I should mention that this is a new set of carbs - my old carbs were running 147.5 jets, and I could only just get a yellow on one carb - after a bit of investigative work I discovered the pilots were the original '42' size, so I'm guessing that pilot sizes will need to be increased on mine to achieve a decent idle mixture.

My new carbs are running standard 137.5 jets and 42 pilots, so I've ordered 4x145 and 4x45 jets (following the 'recommended' sizings) - hopefully this will sort the 'lean' issue.

.... at least, that's my case - your's may be completely different !

Good luck
Chris

[bikerphil]

Brokenarrow, I don't know if you've done this, but make sure your vac. advance is hooked up to the #2 carb and not the intake boot. Is your ign. timing set correctly? I know the model you have is supposedly "tamper proof", but you never know.

[Thee_oddball]

do the "clunk " test on your slides to make sure they are not hanging

[Guest]

hang up

well guys checked sync good-check with propane while tank was off no leaks-made it richer and it got better also a little hesitation between 5000 and 5500 after that she's gone but still hanging up i turned the pilots out 1/2 turn should i go more?
thank you

[Guest]

Pulled carbs

carbs off and the slides drop down fine since their off should i look at anything else??????????????

[Ken Talbot]

slides drop down fine

What would you call fine? Do they snap down immediately when you release them, or do they take a bit of time to creep down? And, do they all do the same thing?

[Guest]

Slides

hey ken well they all come down at the same speed not like free falling they make a whoosh or gurgle sound if that makes sense to you

[Guest]

Slides

ken just went out to the shop and looked at the slides again #1 is a hair slower than the rest should they be falling fast ?i can't remember what my 79 slide speed was maybe the slides need to be polished??

[Ken Talbot]

That sounds about right. The diaphragms control the fall of the slides, so yes, you should hear some sort of a whoosh sound. If they snap down, the diaphragms are leaking for some reason. Sometimes this is from the diaphragm not staying nicely seated in the top of the carb as you try to put on the top cover.

So, hmmm, where to look next....

[Guest]

hang up

ken well slides looked great dropped in with no hang ups sync is great,if i had a vac leak wouldn't it show that? i checked for leaks again with starting fluid and found none, it doesn't hang up between idle and 3000 above that it comes down slow, while riding it will stick at 4000 i can bring it down by down shifting but it's slow,if i hit the kill switch off and on quick it drops down normally. now when i first started the bike and was still cold it had normal throttle response as it warmed up it started to hang up more then running down the road it got worse and stick at 4000?????????????? hmmm is right

[foreda]

Vacuum Advance??

ken well slides looked great dropped in with no hang ups sync is great,if i had a vac leak wouldn't it show that? i checked for leaks again with starting fluid and found none, it doesn't hang up between idle and 3000 above that it comes down slow, while riding it will stick at 4000 i can bring it down by down shifting but it's slow,if i hit the kill switch off and on quick it drops down normally. now when i first started the bike and was still cold it had normal throttle response as it warmed up it started to hang up more then running down the road it got worse and stick at 4000?????????????? hmmm is right

Did you try pulling the vacuum advance off when it does this? Sounds like maybe # 2 carb vacuum or butterfly issue??

[Guest]

carbs

hey foreda butterfly looks good even across what could go wrong with a butterfly? i didn't try pulling vac line off 2 but i did pull the batt and put it in my 79 and went for the first ride of the year!!!!!!!! had to blow off some steam after 3 days on the carbs!!!! i have to pick up another batt and air filter any ways
thanks for the info

[foreda]

Go wrong

Probably nothing but there is a brass seal riveted to the butterflys (at least on my 79 set) and could be easily damaged. I had a similar problem with RPM's hanging in which when it started to rev, I could pull the vacuum advance hose off # 2 carb and it would immediately idle right down. I inspected the diaphrams and found #2 was loose and that I could spin the diaphram on the shaft of the slide. I replaced the diaphram and resync'd carbs and the problem went away.

[TopCatGr58]

I have to ask the basic questions!?

Hey Arrow,

I have to ask. What are the sizes of your main jets, pilot jets? What are your floats set at? What type of gauge(s) are you using to do the vacuum synch? Are you removing the vac. adv. hose during the synch?

Aside from being out of synch, it also sounds like it's running a bit lean, especially as it warms up. When it's cold, it responds to the enrichener okay, but as it warms up, it doesn't respond, hangs!
T.C.