Topic: K0 4 Cable Sync Question - Low pressure Cyl #1

[WideAWAKE]

When I was doing mine I had a problem with my vacuum port/screws leaking air when I attached the brass to attach the hoses from my meter.

I ran some thread tape around them and that solved my problem.

I also ran thread tape on the screws when I put them back in.

[jakec]

The vacuum port is behind the throttle. And the piston is moving up and down making vacuum. So a high vacuum is due to the throttle being closed? Be opening the throttle allows ambient air into the vacuum port, lowering the overall pressure reading?

So to lower the vacuum reading, I need to reduce cable slack in this instance? Am I understanding correctly?

Could anyone confirm or deny this?

[Scootch]

Best thing is to try it. Pull up on the cable at the top of the carb and see what happens. If I remember correctly pulling up on the cable will reduce the vacuum...

[HondaMan]

Thanks! So what carb casting should I have? I just looked at them and couldn't find a number anywhere. I see in this image found on the forum here, the "JN" (jet needle?) setting is "4." Would that mean 4 from the bottom? The #1 needle I took out is in position 3. Being too high though would produce more vacuum, not less..

I also took these pics of the #1 and #2 idle adjustment screws, showing they are basically the same. So the idle sync being good on the gauge and showing visually the same here is a good sign to me (confirming that adjustment is done correctly).

So a fauly #1 gauge.. or a leaky carb boot? Could cause the low pressure? The carb boot because it is after the gauge's intake?

A question for you about these pictures:
Is the hole in the needle jet the same size in both of those pictures? One of them looks bigger than the other. Reason I ask: the needle jets made by Keyster have bigger holes (because their $#@!ing needles are too thick) and if used with the proper Keihin needles will not meter fuel for beans.

[jakec]

I wasn't able to work on the bike for a while. Last night I replaced the oil pressure sensor. I also removed the airbox so I could bench sync the 1/4 throttle open position before starting the bike. I think the carbs were initially bench synced and then got off when I started messing with them.

Anyways when I took the airbox off all 4 intake boots had a little fuel on them. So that fact combined with the intermittent leaking, I'm going to take the carbs off tonight and redo float heights. I have all new solid black plastic floats. I'll also take a look at jets and tubes while I'm there.

[BenelliSEI]

The vacuum port is behind the throttle. And the piston is moving up and down making vacuum. So a high vacuum is due to the throttle being closed? Be opening the throttle allows ambient air into the vacuum port, lowering the overall pressure reading?

So to lower the vacuum reading, I need to reduce cable slack in this instance? Am I understanding correctly?

Yes….. you have all of the above correct. On my K0 I had all the issues you describe (it made me 1/2 crazy) UNTIL I sealed the carb tops with a gasket. Don’t worry about getting the correct ones. I used K1-6 style, just knocked about a 1/2” hole on centre, with a gasket hole punch. ALL my problems went away.

[Scootch]

+1 on the gasket at the top of the carbs

[jakec]

Yes….. you have all of the above correct. On my K0 I had all the issues you describe (it made me 1/2 crazy) UNTIL I sealed the carb tops with a gasket. Don’t worry about getting the correct ones. I used K1-6 style, just knocked about a 1/2” hole on centre, with a gasket hole punch. My problems ALL went away.

Thanks for the clarification. I also just went ahead and ordered a set of the top gaskets for a few $ each on ebay.

[BenelliSEI]

Good move. Will be interested to hear the outcome. I also check out what Mark commented on.

[jakec]

I just rechecked my floats. They were all dead on compared to my gauge which is 27mm. I know the setting is 26mm. But I made this gauge a long time ago and i think it’s just a little off (slightly less than 27mm). Too large of a reading would give less fuel anyways.

I’m wondering if the problem could be related to using the black floats? They’re the same circular shape as the brass ones but maybe they’re less bouyant by volume? So the reading should be even higher?

All the valves and seats were clean although the valves do have a slight visible wear to them, and the springy part is not consistent across all of them. I looked into getting some OEM valves and looks pretty pricey. It’s also not something I think I’ve ever had to replace.

My symptoms have been occasional burp of gas out the #2 overflow drain, very slow leak out the #3 drain screw, and slight wetness on intake boots after sitting 2 weeks with petcock off.

The bike was running fine before so this isn’t really necessary for figuring out my carb sync, but I do want to fix it while the carbs are off.

[jakec]

Also I removed one of the needle seats like Marc was talking about, and it doesn’t have any stamps on it. The jets are originals though with the K stamp on them.

[jakec]

Here’s a pic of the float valve wear.

[Scootch]

I'll throw this out there fwiw... I just did a carb rebuild on my K0. I bought the kit from Yamiya. It has everything one needs to refurbish the K0 carbs. 3 different sizes of jets, needles, brass floats, valves with rubber tips, idle jets, gaskets, etc. I think it was around $150. I took their advice and used the #110 main jets and the needles set on the mid position. I took Mark's advice and opened the specified emulsion tube  holes to 1 mm. Set the float height to 26 mm. Did the carb sync in a matter of minutes. My machine is running very well. It idles nicely. Consider giving the Yamiya kit a look...

[jakec]

I see that kit is $110. Not bad. I'm pretty sure if anything though I only need the float valves. It looks like the valves are the later style with the rubber tip. Is that what you used? Since the yamiya kit is aftermarket anyways I may just get new valves.

[RAFster122s]

Definitely need new float valves for the bike.

The valves have a very thin band ground for the seats, less than 1/16” band/width of the seat…got photos of your valves?

David

[jakec]

I guess I'll bite the bullet and get NOS for the valves. No pic of the seat right now, but if they need to be replaced as a set I guess it doesn't matter. $111 for an NOS set 

[Scootch]

I see that kit is $110. Not bad. I'm pretty sure if anything though I only need the float valves. It looks like the valves are the later style with the rubber tip. Is that what you used? Since the yamiya kit is aftermarket anyways I may just get new valves.

Yes the kit from Yamiya has a rubber or neoprene tip.

[RAFster122s]

Have someone like MReich or HondaMan take a look at photos of your valve seats and your valves. Depending upon condition you may have usable valves. Seats often can be given 3way aserdi valve job. KibbleWhite valves can be good option...or stock Honda. The Honda units aren't F valves so they tend to last longer...

[robvangulik]

Have someone like MReich or HondaMan take a look at photos of your valve seats and your valves. Depending upon condition you may have usable valves. Seats often can be given 3way aserdi valve job. KibbleWhite valves can be good option...or stock Honda. The Honda units aren't F valves so they tend to last longer...

This discussion is about float valves now...

[jakec]

Haha. Float valves arrived today. I will install and see results. Then waiting on the gaskets to arrive next week hopefully.

I don't think there's anything wrong with the needles and seats because there was no problem with the throttle response before I messed with the carb sync.

[jakec]

Installed new seats. They are stamped 2.5 instead of 2.0 like the old ones. Part number matches though. I also reset the floats to a true 26mm. Installed and so far so good, I’m waiting on the top gaskets now.

I’m debating getting a new throttle cable. NOS aftermarket is $30. Real NOS is $75. The bike also came with another throttle cable that has the exact same damage. I think it gets messed up from the tank sitting on it. Initially I declined to get a new cable because I figured it’ll just happen again. It moves smoothly.

[jakec]

I found an old NOS motion pro cable for $15 on ebay. And I modified the carb top gaskets with scissors. Installed both. Will get around to doing the sync one day..

[jakec]

I think I’ve nailed down my problem. One of the hoses is bad. I swapped the hoses around as well as the restrictors in the hoses, and the problem (low pressure when doing 1/4 throttle exercise) always followed one hose. I was able to do the idle sync but once the pressure spikes from the 1/4 throttle this one hose loses all pressure.

So need to figure that out and then hopefully it’ll be easy.

[jakec]

Also I’m still getting this random burp of gas out of the 3 & 4 carbs, maybe every 5-10 min out of the drain hoses. Not sure if that’s due to the 2 hose petcock design.

[Ujeni]

Might be time to make sure your manometer is calibrated. Easiest way to do that it to make sure that each dial (I assume you have a four-dial or four-tube manometer) registers the same value on the sam cylinder. Hook each tube one at a time to the same cylinder and make sure you are getting the same value. Might be time to upgrade your manometer too. I have a carbtune pro and really like it so far. My old dial gauge still works well too.

On the leaking fuel, your float valve or valve seat is bad. Take out the carbs and and clean or replace them. Then double check your float levels.