power loss

[detorn]

(please read before you respond)


So I've been working on this bike for a couple of months now. This is my latest issue.

After cleaning and rebuilding the carbs the bike was running okay, not great but okay. I could tell visually that carbs 2 and 3 were not connected to the air intake all the way so I took the time to make sure everything was connected right.

Now when I roll on the throttle there is noting. It runs up a little bit but levels off very fast, and even loses power as I progress up through the gears. When the bike is parked after trying to ride the hose that comes from the plastic box that connects to the carbs drips fuel. The carbs are clean, the plugs are new, the o-rings are new, the air filter seems to be in good shape. The wires that connect to the plugs all work too.

Any ideas on what could cause this power loss along with the fuel leak? When just the two carbs (1 and 4) were connected, everything ran good enough.

I'm looking for trouble shooting tips in order of most likely.

The petcock is good also I should mention.

I think it is an air leak somewhere, but have no idea where it could be or how to test that hypothesis.

Any help would be huge.


Thanks

 

[detorn]

pipes, carbs, and everything else on the bike is stock.

 

[almarconi]

Did you set your float height correctly? Did you bench sync and vacuum sync your carbs. Have you adjusted your valves?

In terms of air leaks, have you replaced the intake holder o-rings? Are the carbs to intake boots and the carb to airbox boots in good condition?

To check for air leaks, spray some carb cleaner or WD-40 on the carb intakes and listen for any rpm changes.

Now when I roll on the throttle there is noting.

What does noting mean?

 

[detorn]

I've checked for leaks around both sets of boots with carbs cleaner. Floats are set to factory spec. Have not checked the valves, but there are not enough miles on the bike for that to really be an issue. Carbs have been bench synced, but not vacuum synced. I had a fellow board member help me with the carb rebuild (he has done the job enough that I'm confident in the work he has done) and was planning on riding down to him to do the vacuum sync once I reinstalled the carbs.

Just to be clear, I wasn't losing power till after I hooked all of the carbs back up. This wasn't an issue before I did the rebuild. I had a fuel leak problem that I thought was the carbs, but found out it was just the vacuum hose had come off. But since the carbs were off at that point I did the rebuild anyway.

The mechanic tried pulling the plug wires one at a time while the bike was running, each resulted in the bike stalling (I don't know what that means, just figured I'd mention it since he did it).

I'm going to take another look at the air filter, air box, and intake books tomorrow. Maybe even check the plugs again even though they are new.

Any other ideas on what could cause gas to kick back to the air intake?

 

[sk843143]

i have the same symtoms..... only coupled with hard cold starting .... i have tracked it down to posably the valves need adj..... (its a maintnece item that should be done anyway .)

 

[Charlie G]

Detorn,

Sounds like you having a rough time getting it running right. My first thought when you said that fuel was running out of the airbox drain was that the petcock was bad or set on prime. How much fuel? You say the petcock is ok. New or rebuilt? Does your oil smell of fuel? Wish you luck!

Charlie G.

 

[Guy]

Just to be clear, I wasn't losing power till after I hooked all of the carbs back up. This wasn't an issue before I did the rebuild. I had a fuel leak problem that I thought was the carbs, but found out it was just the vacuum hose had come off. But since the carbs were off at that point I did the rebuild anyway.

There shouldn't be fuel coming through the vacuum hose.
Are you sure you have all the hoses connected up properly and haven't mixed up the feed/vent/vacuum lines?

 

[detorn]

Detorn,

Sounds like you having a rough time getting it running right. My first thought when you said that fuel was running out of the airbox drain was that the petcock was bad or set on prime. How much fuel? You say the petcock is ok. New or rebuilt? Does your oil smell of fuel? Wish you luck!

Charlie G.

The petcock is not new or rebuilt. I assumed it was not the problem because fuel does not leak while the bike is off, just after it has run for a while.

There shouldn't be fuel coming through the vacuum hose.
Are you sure you have all the hoses connected up properly and haven't mixed up the feed/vent/vacuum lines?

These hoses are different sizes, so it is not possible to put them on wrong.

 

[gggGary]

If there is fuel dripping after running something is not stopping fuel flow the way it should. Most likely culprit will be at the float valve. Either a piece O crud showed up and is blocking a valve open or a new O ring didn't seat right but again the float valves is where to be looking. Running the bike with raw gas washing down cylinders is not a good idea. A hydro lock is a real possibility also.

 

[detorn]

If there is fuel dripping after running something is not stopping fuel flow the way it should. Most likely culprit will be at the float valve. Either a piece O crud showed up and is blocking a valve open or a new O ring didn't seat right but again the float valves is where to be looking. Running the bike with raw gas washing down cylinders is not a good idea. A hydro lock is a real possibility also.

Is there anyway to test this without pulling the carbs completely apart again?

 

[gggGary]

I cruised much of your other thread and it seems like you still have the problem that caused the PO to sell the bike to you. Bad news? yeah the carbs will have to come off again. Good news? every time you do it, it gets easier. I used to be able to pull a set of KZ1300 carbs out of the bike and on the bench in 15 minutes flat. (3 - 2 barrels) The 64 thousand dollar question is what kind of shape the float valves are in. It is easy to muck up float valves removing them to replace O rings. To be blunt most likely at least one of them is AFU It can be very subtle and hard to see, so if it were me I might try pulling the air cleaner boots and try to figure out which carb is actually the leaker and put a new float valve in that one.
There used to be an Aussie or Kiwi who had an inside line to Mikuni or one of their suppliers who could ship float valves to the US fast and cheap. He advo'd on flea bay but that was a few years ago.

 

[gggGary]

PS did you ever set the valves? All bets are off if you haven't done that. It's becoming one of my rules, no old bikes that don't have screw style tappet adjustments. To help enforce that I sold off three different sized (25, 29, 29.5mm) sets of valve shims to reduce temptation!

 

[teddux]

You can try removing the vent/overflow tubes from each carb and set petcock to "prime".

The one(s) still overflowing, you may try to remove just the sumps/check valve in situ?

 

[Guy]

These hoses are different sizes, so it is not possible to put them on wrong.

Vent and supply spigots on the carbs are the same size, and it's not unknown for lads to mix them up..

 

[detorn]

update:

I got the carbs off again, and you were right, it was easier this time.

I picked up a new fuel hose. I ordered it a while back. The hose that was on there was wet with fuel. The new one fits a lot more snugly.

I double checked the petcock with the new hose to make sure it was okay. It performed as desired.

I checked the plugs, the were a little off color, but looked okay.

I should mention that there is a little too much oil in the bike. I will drain it down tomorrow. Also, the oil pressure light is lit, I chalked this up to a short and didn't think twice about it, but maybe these two things are related.

I will check the float heights tomorrow once the carbs dry out a little. I have to say they are super clean though. So if it is not the float height I'm at a loss.

Air intake boots are clean and pliable, engine boots look good too.

 

[detorn]

Vent and supply spigots on the carbs are the same size, and it's not unknown for lads to mix them up..

Hoses were on right, however, I do think I misidentified where the fuel was leaking from. Once I check the float heights and get the carbs back on I will double check that all of the lines are run correctly.

 

[almarconi]

I should mention that there is a little too much oil in the bike. I will drain it down tomorrow. Also, the oil pressure light is lit, I chalked this up to a short and didn't think twice about it, but maybe these two things are related.

You've probably got gas mixed in the oil.

 

[waterman]

I have mounted the rack of carbs in a bench vise and by using an auxiliary fuel tank I have checked fuel level in the carb bowls. You may want to try this setup to see if you have a float valve that is not shutting properly, just look for a gas seeping out of throat. Likewise if you have a bad float, it will show up also. The hard part about mounting rack is getting the correct angle that the carbs sit at in bike.

 

[detorn]

You've probably got gas mixed in the oil.

No gas smell in the oil. I just added too much oil. Going to do an oil change either way.

 

[detorn]

so I took it all apart. The floats were all working and at the proper height. I put it back together, taking my time and really sweating the details and its better.

There is still a slight hesitation, but it is not bogging down like it was. I was able to get up to speed and ride safely on the streets. There is no fuel leak from any of the overflow hoses.

Still slow off the line, but when it picks up you notice...

Thank you all for your suggestions.