Topic: Everything was going so well until today

[fizzlebottom]

I fully rebuilt my carbs, did a bench sync, reinstalled, and have ridden a few times in the last 2 weeks. I got the chance today to do some final adjustments. Got the cam chain tension and valve clearances all set. Took it for a ride and EVERYTHING was perfect except the idle was less steady than I want. Got home after the engine was fully warmed up and got to vacuum syncing the carbs.

I've got the Emgo 4 gauge sync tool with damper valves. Hooked it up and got to syncing. Got all 4 cylinders matching according to gauges and now it idles too high and can't go down any further. Additionally the idle creeps after a minute and isn't nearly as responsive when blipping the throttle. I think the root of my problem is old possibly cracked vacuum hoses and sync tube O-rings and gauges that aren't adjusted against a single vacuum source.

The absolute last thing I want to do is remove the carbs and bench sync again only to get 80% there again. They're such a hassle to remove and reinstall. Think I might just take it over to the shop down the street and let them fix me up.

Just needed to rant. I was so close to having no worries for a while. It's a small issue in the scheme of things, but man it feels like a had it at my fingertips.

[caluser2000]

What is the bike?

Our oldies garbs had a throttle sop screw on them to riaise or lower the rpm.

Did you sync to match syenc. 1s vacuum pressure?

[fizzlebottom]

It is an 82 CB650SC with VB44C carbs. The idle screw is out all the way after this failed vacuum sync attempt. Can't get idle below 1500 now in addition to a slow creeping increase till I blip the throttle and let it settle back down.

I just did a crude check on how closely the gauges match each other with a pressurized brake bleeder. They seem to be pretty spot on with each other, but I think my hoses are not sealing correctly or the brass sync tubes were not sealing to the carb vacuum ports with the O-rings. I might invest in some pluggable vacuum port screws for the future.

[caluser2000]

It is an 82 CB650SC with VB44C carbs. The idle screw is out all the way after this failed vacuum sync attempt. Can't get idle below 1500 now in addition to a slow creeping increase till I blip the throttle and let it settle back down.

I just did a crude check on how closely the gauges match each other with a pressurized brake bleeder. They seem to be pretty spot on with each other, but I think my hoses are not sealing correctly or the brass sync tubes were not sealing to the carb vacuum ports with the O-rings. I might invest in some pluggable vacuum port screws for the future.

Try adjusting the pull and return  throttle cable back a bit. I the throittle quadrant returning fully to the return stopper whenthe  throttle is closed?

[fizzlebottom]

I checked the throttle cables after my sync attempt failed. Throttle freeplay is within spec, both cables move freely without binding, and they fully return when closed.

I'm really inclined to believe that either the vacuum sync hoses were leaky or that the adapters were not sealing against the carb body at all. I checked the O-rings after and they looked pretty gnarly.

I also think that due to the apparent vacuum leaks, right now the #2 butterfly is closing all the way but #1 and #3 (therefor #4 as well) are way too open. Those 3 are keeping the idle high and really uneven, and #2 is letting the idle screw come all the way out.

I'm tired of fiddling for now and just want to have a good riding season, so this one is being left to the paid pros with better shop gear than I've got.

[Kevnz]

Assuming the shop has the expertise as well as the equipment. Not always a given. Good luck.

[caluser2000]

The home made manometer I made using a 4 aquarium taps, a cheap car vacuum gauge and  about 5mtrs of vacuum tube had my CB550s old card sync perfectly. Bike got quieter than its ever been at idle. If just took a bit of time to get there that is all.

[fizzlebottom]

Assuming the shop has the expertise as well as the equipment. Not always a given. Good luck.

Its a Honda Powersports shop and they usually have a good number of older bikes in the service area when I've been there in the past. Might not be SOHC4 specialists, but I called and they didn't hesitate to say they can do it.

[caluser2000]

If the O'rings on the adapters are just dry and not cracked uswe a bit of CRC 556. It refreshes the rubber O'rings. I found this out quite accidentally years ago.

[fizzlebottom]

If the O'rings on the adapters are just dry and not cracked uswe a bit of CRC 556. It refreshes the rubber O'rings. I found this out quite accidentally years ago.

They were cracked. No coming back from that. I don't have a bunch of spares sitting around either. Oh well.

[Pappy]

Well...... You have sure tried to help me through my issues......If you were closer I would do that job for you.
I have a digital sync tool that works perfectly and is easy to use for up to 6 cylinders.
Lesa and I both have Valkyries which are opposed  6cyls.  and carbed.

[fizzlebottom]

Well...... You have sure tried to help me through my issues......If you were closer I would do that job for you.
I have a digital sync tool that works perfectly and is easy to use for up to 6 cylinders.
Lesa and I both have Valkyries which are opposed  6cyls.  and carbed.

Thanks for the thought. These bikes are blissful when they're running great and maddening when they're not. This one is definitely my fault for using the sync tool without checking it's condition. I've got a Wednesday appointment to get it all sorted at the local shop. I'm due for a new helmet and bluetooth comm system, so this cost will he a drop in the bucket.

All in the name of a good riding season out here in the PNW.

[Pappy]

Friend of mine once said..... "What's money when your heart ain't in the right place"

[fizzlebottom]

I know you're all just sitting on the edge of your respective seats waiting for an update, so here it is.

Yesterday I replaced all those pesky cracked o-rings on my sync gauge rods and got some new hose. I got those gauges reading so exactly the same that I'd challenge even an expert to do better (they definitely could). Still idles worse than before I started vacuum syncing.

So I decided to do what any sane person here would do. Instead of taking the bike to the Honda shop like I said I would, I took the carbs back off the bike a few mins ago and have resolved to fix this #$%* myself. Carbs are off and I have two new bits of info that may be culprits:

1. Prior to reinstalling them, I soaked the insulators in a mix of wintergreen oil & alcohol. There are no cracks and they went on super easy. But they may have swelled some, and I didn't snug the clamps after the swelling went down. They very well may have been slightly loose after a few weeks.
2. Two of the throttle butterfly screws were loose! When I reassembled the carbs, I very well may have neglected to tighten them appropriately. Like a dummy. I think one of the butterflies was not square in its bore, causing true synchronization 100% impossible.

I did a bench-sync again. It is chilly out, so the insulators are soaking in the mixture a little bit more with some heat. Going to get them soft and warm and pop everything back together either later today or tomorrow morning.

Gremlins, man. I'm determined to get this bike running like a top. Need to justify investing in this nice Cardo Freecom 4+ and the new helmet to come.

[Bodi]

Not familiar with CV carbs, but on slide carbs some types have one sync unadjustable, and you sync using the other three.
For those with all four adjustable it is easy to get perfect sync, but have adjusted the overall height of all four so the idle screw is out of range. And the choke throttle cam doesn't work any more.
Is that a possibility with yours? If so adjust all four sync screws to just close their throttles fully with the idle screw about 1/4" out, then resync while only adjusting three carbs. That should give you the range needed to have full idle control. If they have a choke idle advance, that probably needs adjustment as well.

[fizzlebottom]

Not familiar with CV carbs, but on slide carbs some types have one sync unadjustable, and you sync using the other three.
For those with all four adjustable it is easy to get perfect sync, but have adjusted the overall height of all four so the idle screw is out of range. And the choke throttle cam doesn't work any more.
Is that a possibility with yours? If so adjust all four sync screws to just close their throttles fully with the idle screw about 1/4" out, then resync while only adjusting three carbs. That should give you the range needed to have full idle control. If they have a choke idle advance, that probably needs adjustment as well.

CV carbs (at least these ones) are synchronized against carb #2, which is not adjustable. To sync, you start by matching #1 to #2, then #3 to #2, and then #4 to #3. Bench sync can be done with a really small drill bit, but I don't like letting the butterflies rest on a hard surface like that. I match the reflection of the slow jet holes on the butterflies. It gets close enough to get the bike running and ready for vacuum sync (with quality tools).

[caluser2000]

At least you've found out what the probble issue is fizzlebotten. PeWe listed some good locktite types to use on verious components in another thread. Maybe he could recap that info in this one.

[fizzlebottom]

Update #2

I'm tentatively claiming to have fixed the problem. Got the carbs reinstalled. Fired it up. I'm extremely surprised how little choke it needed given the 47 whole degrees it is outside. Adjusted idle to 1k, and it is idling smoother than it ever has in my possession. I let it warm up for a few mins and blipped the throttle. Went up to 8k no problem, came back down quickly, and remained at just a smidge above 1k. It is also way quieter. I think my bench sync was much closer this time.

I need to ride so badly now. Motorcycles are pure happiness.

[caluser2000]

Indeed they are. Pure joys when running correctly.

[Pappy]

Well done!
I know lots of folks who soak their insulators in the same solution. None that I know of have had the same issue. Going to ask one of the guys in another forum if he has ever run across it after a good soaking and some time on the road. May be a good tip to keep in mind.

[34barab]

Curious about the wintergreen oil/alcohol solution.  Ratio?  How long do you soak them?

[BenelliSEI]

You are probably doing this, but just in case......

I always start with all four gauges hooked up, via their long hoses, to a single carb. Single hose, to a multi barb connector. Start up, adjust and ensure all 4 gauges read IDENTICALLY. Then switch them over to 4 separate carbs. Also, make sure the restrictor in the line is at the carb end, not at the end attached to the gauges.

[fizzlebottom]

Curious about the wintergreen oil/alcohol solution.  Ratio?  How long do you soak them?

1 part wintergreen oil to 3 or 4 parts rubbing alcohol. Soak overnight at least if they're pretty hard. Check for swelling afterwards.

You are probably doing this, but just in case......

I always start with all four gauges hooked up, via their long hoses, to a single carb. Single hose, to a multi barb connector. Start up, adjust and ensure all 4 gauges read IDENTICALLY. Then switch them over to 4 separate carbs. Also, make sure the restrictor in the line is at the carb end, not at the end attached to the gauges.

I tested the gauges against each other using a manual vacuum pump. They checked out fine. I'm probably going to leave them alone after this debacle. Things are running smoothly, so no more fiddling. Only riding.

[Deltarider]

You are probably doing this, but just in case......

I always start with all four gauges hooked up, via their long hoses, to a single carb. Single hose, to a multi barb connector. Start up, adjust and ensure all 4 gauges read IDENTICALLY. Then switch them over to 4 separate carbs.

I have once done that in the past and it turned out to be a mistake. If we talk gauges, meaning mechanical underpressure clocks, calibrating cannot be done simultaneously, as the moving membranes will interfere. I once tried this with my set and judged the clocks were off. Took the set to where I had bought it and the man demonstrated with a stabil (non pulsating) vacuum pump, there was nothing wrong with them. So if you want to calibrate clock gauges simultaneously, you'll need a non pulsating vacuum and certainly not a running cylinder. The only way to calibrate with a running cylinder, is to connect them one after the other to that carb. Or do it, as said, static with a stable, not pulsating vacuum pump.
I always regretted I spent that money on that set. Since I've developed my own method of syncing, I have semi-donated my set to a befriended mec, who had helped me a great deal with my marine diesel.

[caluser2000]

You are probably doing this, but just in case......

I always start with all four gauges hooked up, via their long hoses, to a single carb. Single hose, to a multi barb connector. Start up, adjust and ensure all 4 gauges read IDENTICALLY. Then switch them over to 4 separate carbs.

I have once done that in the past and it turned out to be a mistake. If we talk gauges, meaning mechanical underpressure clocks, calibrating cannot be done simultaneously, as the moving membranes will interfere. I once tried this with my set and judged the clocks were off. Took the set to where I had bought it and the man demonstrated with a stabil (non pulsating) vacuum pump, there was nothing wrong with them. So if you want to calibrate clock gauges simultaneously, you'll need a non pulsating vacuum and certainly not a running cylinder. The only way to calibrate with a running cylinder, is to connect them one after the other to that carb. Or do it, as said, static with a stable, not pulsating vacuum pump.
I always regretted I spent that money on that set. Since I've developed my own method of syncing, I have semi-donated my set to a befriended mec, who had helped me a great deal with my marine diesel.

Deltarider your logic seems to defy logic.

Oh well, each to their own I guess,

I'm deeply sorry for your loss,,,,