Topic: Odd timing issue, the closer to F the worse it runs.

[carnivorous chicken]

Sorry if I missed it -- haven't gone back and reread the entire thread again -- but have you synced your carbs? Have you checked for air leaks on the carb boots? Is your tank vent blocked causing fuel starvation issues? Timing it at 3000rpm isn't going to work as others have suggested, it's got to be around 1200-1300rpm to line up with the marks.

[Jore]

Sorry if I missed it -- haven't gone back and reread the entire thread again -- but have you synced your carbs? Have you checked for air leaks on the carb boots? Is your tank vent blocked causing fuel starvation issues? Timing it at 3000rpm isn't going to work as others have suggested, it's got to be around 1200-1300rpm to line up with the marks.

Carbs are bench synced for the moment, carb boots are new (about 2 years tops), no air leaks that I know of, I have sprayed carb cleaner around the carbs and nothing has changed and the bike stops once you block the air intake passage from the airbox.

[BomberMann650]

To repeat what has been said; If the timing is off, the motor will rev up.

If things are revving smoothly, you should be able to rotate the entire timing plate to get things bang on. 

[TwoTired]

I had no time to mess around with the bike today, but I did give it a quick start up, the revs went sky high!
What could cause that?

For one thing, the slides being held open.

If the slides can't reach the carb bore floor, the idle knob can't adjust proper idle speed.  This is often the result of an improper bench sync using a drill bit or allen key.

[Jore]

I had no time to mess around with the bike today, but I did give it a quick start up, the revs went sky high!
What could cause that?

For one thing, the slides being held open.

If the slides can't reach the carb bore floor, the idle knob can't adjust proper idle speed.  This is often the result of an improper bench sync using a drill bit or allen key.

And that's exactly what I did, I'll pull the carbs off again and do it correctly this time.

[Jore]

I bench synced the carbs again as per the instructions given to me, and this time she idles nicely, I think part of the problem was the nut on the high idle screw becoming loose and that made the carbs slides open up way more, she's tight for the moment and I'll sync the carbs with a set of diy manometers for the moment, here's a short video on how she runs:

[Jore]

Tried vaccum syncing, I think my setup isn't ideal, so I whipped out a vacuum gauge I had lying around and measured each cylinder, from left to right the first one pulls about 7 inches of mercury, second and third 6 and the fourth one fluctuates a bit from 7 to 10 depending on the revs, I know this measurment isn't ideal, but at least it's a start, the screws are turned all the way to the right on the screws. But I think I'm doing something wrong, the honda manual is kinda vague on the subject. I do remember when I originally got this bike that the mechanic who checked it vacuum synced it and iirc loosend the brass caps on the linkage befor doing it, can anybody tell if this is the correct way of doing it?

[carnivorous chicken]

The 400F sync is performed with the tank off and the four adjusters (they look like threaded studs with slots on top) and lock nuts that are two each in between the 1 and 2 carbs and 3 and 4 carbs. They have to be adjusted at the same time -- or at least that's the easiest, as adjustments in one can cause changes in others. Not sure which screws your turning all the way to the right -- idle mixture? -- but the ones you want are on the top side of the carb, next to the caps on each carb. Carbtune tool is what you want -- the exchange with the British pound makes them more affordable now. OR mercury. I don't use gauges but others like those. Motion Pro are crap.

** quick edit: 350F to 400F -- same adjustment procedure.

[TwoTired]

You need 4 vacuum gauges (or manometers) as the vacuum levels are transient as adjustments are made, and engine speed changes.

You should get a shop manual for the bike if you are going to work on it.

[Jore]

This is the setup I'm using for the moment:


Sorry for the bad quality but it was kinda late and had bad lighting, I'm using atf for the liquid and .030 mig nozzles as restrictors.

I do have a shop manual and I'm adjusting the correct part, but I have them all the way down mostly, I'll see if someone can lend me a set of proper vacuum gauges, since those things are expensive to get down here.

[strynboen]

yes you need a 4 manometer set...and a strong air blower..to have some time to do the job..the engine runs hot in a few minuts..in the film i move the line from one meter ..to thek it gives the same resultat in all 4 intakes..

that atf fluid..is just a oil vaste..all over the place.

..cant get somone vill use that system..try to seargh on e bay its not a expensive set..but if it are calibrated korrekt its fine..far better then fuel lines full of oil..dripping all over you shop..in the NeXT month..to you throv it aut...
i also have bayed that special schrevdriver to both hold and adjust at the same time..you can build one..use a some old tools..

[flybox1]

If you are running out of adjustment room on the vacuum sync screws, Its an easy step to 're-set' them.
Take the carbs off the bike.
Adjust all vacuum sync screws so there are 4 threads of screw showing out the top of the adjuster nuts.
Perform another bench sync.
Complete the vacuum sync.

[Jore]

yes you need a 4 manometer set...and a strong air blower..to have some time to do the job..the engine runs hot in a few minuts..in the film i move the line from one meter ..to thek it gives the same resultat in all 4 intakes..

that atf fluid..is just a oil vaste..all over the place.

..cant get somone vill use that system..try to seargh on e bay its not a expensive set..but if it are calibrated korrekt its fine..far better then fuel lines full of oil..dripping all over you shop..in the NeXT month..to you throv it aut...
i also have bayed that special schrevdriver to both hold and adjust at the same time..you can build one..use a some old tools..

Thanks, is the tool something like this?

[Jore]

If you are running out of adjustment room on the vacuum sync screws, Its an easy step to 're-set' them.
Take the carbs off the bike.
Adjust all vacuum sync screws so there are 4 threads of screw showing out the top of the adjuster nuts.
Perform another bench sync.
Complete the vacuum sync.

Thanks that shouldn't be too difficult to pull off then.

[flybox1]

That tool makes adjustments quick and easy    Glad I have mine.

[strynboen]

yes exact that..i have used it on my 550 too..but had a problem to get to the carb under the frame tube..but still a good tool

[Jore]

I made the manometer work after fiddling a while, this is about as close as I got the carbs:

[scottly]

That should be close enough for now; certainly not enough variation between cylinders to cause major running issues.

[BomberMann650]

They remained steady enough for a photo!  Good work.  Hows it idle now?

[Deltarider]

Jore, that's excellent. First time I see them that close. Compliments!

[Jore]

Thanks I fiddled around with them a bit, i used some aquarium valves and if I cracked them open just a hair they seemed to maintain everything pretty steady if they where open fully the atf would jump around it even got sucked in a few times, here's some previous attempts of syncing them:



all in all it took me about half an hour to get things to run smoothly, the bike idles pretty fine I can even get it down to about 800 rpm, but i'm setting it somewhere around 1100, that's where it sounds better, I'm still going to recheck timing and the idle screws.

[carnivorous chicken]

Idle should be set at around 1200 on those things IIRC. Congrats on getting that dialed in.

[Jore]

So I took the bike out for a ride, probably about 10 km long, I must say I'm a bit disappointed, the tach cable broke so I wasn't able to see accurately the revs but to me it left like she would bog down at around 5-6 k, the quickest I could ride her was about 60 km/h and that was in sixth gear, after the carb sync I haven't touched the timing could that be whats causing the low power?

[carnivorous chicken]

So I took the bike out for a ride, probably about 10 km long, I must say I'm a bit disappointed, the tach cable broke so I wasn't able to see accurately the revs but to me it left like she would bog down at around 5-6 k, the quickest I could ride her was about 60 km/h and that was in sixth gear, after the carb sync I haven't touched the timing could that be whats causing the low power?

Yes, among others. Time it at a proper idle speed of 1200 and go from there. While you might be able to shift into 6th at 60KPH, you probably shouldn't until you hit something closer to 80-100KPM. These bikes like to rev high and they purr at 5-6000RPM or higher.

[BomberMann650]

What do you mean by "bog down".
To me, that would mean too much fuel, not enough air.  Like trying to ride with the choke on. 
There is a known "flat spot" issue with these honda fours.  If it felt like a loss of power, and no amount of throttle twist would get er goin.  That is typical of a lean condition.
Depending on the carbs, richening at the air/fuel mix screw can let more fuel make it through the carbs.  Then it should be able to power through the revs.
Should.
If that doesn't work.  Check the needle clip position and main jet sizing (again?)