low compression in one cylinder,

Filling the chambers with gas or oil and letting it sit does not indicate a good valve seal. The surface tension alone can hold the liquid in the chamber forever. Wipe off the valve and seat your testing very clean. Insert the valve, push down on it and twist it back and forth. Fill the chamber with water and push down on the valve. Insert an air nozzle with a rag wrapped around it into the port and pull the trigger. There will be bubbles. There should be NONE. Bent valves will MOST always leak very rapidly (bubbles). If you suspect one take it to the shop and have them put it against the stone. It will skip off and on the stone if it's bent. I use course grit or medium grinding compound to lap. Don't lap any valves that common sense rules are possibly bent. They will groove and will be heavy on one side, light on the other (the margin). Watch the margin form on all of them, it will widen as they get closer to set. The bubbles will become less at the same rate as the margin widens and becomes more bold, sharp and wide. Any head will leak right off the machine shop shelf if you apply air to the port. This method is the reverse direction of the way everone else does it. It puts the seal to the test. It's the way to the seal. You do all these steps and I assure you: When you add oil to the cylinders for compression check, the psi numbers will go through the roof. This is false and temperary reading, but it ensures an excellent valve seal. It can also mask ring problems (until the oil is gone), but then you know what you have for valve seal. U may have tapped a valve or two. My opinion is if you had, the compression would be lower than 100. More like 60psi or 0psi. Ask the machinest what grit stones he used in the hone. Also, rings sometimes won't seat for a little while then bam, there in. The numbers go way up, just like that. U have earned yourself the perfect opportunity to check and fix any valve issue. It's such a relief knowing exactly what you have. No guessing no confusion. Just rock hard science. Ask Old Man Rock! The most scientifical sonofagun EVER. BUT if we have a question he WILL have an answer. Rock on brother and good luck!

Make sure all four bowls have fuel by looking at the plugs for gas that didnt burn. Feeling the pipes will show if all cylinders are working or not. If it started, ran, then quit and won't start again, u may have fouled out the plugs. Especially if one or two were already fouled. Could be the reason it quits. Sometimes gas does'nt make it over to the right hand or left hand set of carbs due to the fuel line being to low or the float needle sticking in the seat from cleaning and not getting all the resin off the parts. It could also be a bad electrical connection at one of a few key places that are common. Let us know what goes on.

One thing I'm not seeing in this post is if the valves are old or new..... Nor do I see if new head components were installed such as springs and guides.... It just may be a crappy valve, not necessarily bent but just crap....

Here's why I say this....
Had my head work accomplished by the man himself, Larry C.... Now Larry had informed me from the beginning, replace the valves regardless... Unfortunately being a dumb ass and tried going cheap, I didn't listen... :blush: Yeah I know, I know...

NOTE: My issue as being depicted below had NOTHING to do with Larry or his work!!! This was totally out of anyone's control and if anything, it was MY DOING!!!

Within/during the first 6 months, the engine smoked more then expected and in my engine break in periods, during my valve clearance measurements I found #1 exhaust would not hold it's clearances like the others.... WTF you say.... Swapped out the shims twice and same thing each time I measured...

Contacted Larry and informed him my bad, just let me know the costs after inspection, I was sending the head back with new exhaust valves and OEM seals. Yup, tried going cheap on the seals originally as well... Stupid MF I was....

See, when I didn't carefully listen to the man, upon initial inspection, the intake valves were shiza and required replacement... Larry Informed me the exhaust seemed ok but based on experience alone I should replace them especially based on intake conditions... Well of course didn't listen (I've since learned to listen to the man) I got cheap (dumbass) and said ah shit, leave them in.... :blush: :pinch: :whistle:

Learned the hard way, something was just not right about that #1 valve, just wouldn't seat properly.... Replaced with new Kibble White valves and OEM seals, Larry performed his magic and in 2500 miles (4000 miles total now), clearances as expected and no smokey...

Little 1015cc w/performance cams & 29mmm CR's pulls like a mo foe.... :evil:

Sorry for the long story all but it's totally true at that... Sometimes these old valves and head components have seen their time... Just crap after 30 years of abuse.... As explained to me by Larry, they can go soft, they can slightly deform when hot, they can be some after market unknown crapola... who knows for sure...

Just my 2 cents anyways... Hope you get it resolved...

OMR

Is this still injected or carbureted now?

If injected, the most likely suspect is the ECU or a bad wiring issue.

There's code light on that system. Little light on the ECU itself that will flash. Codes are in the GPz11 supplement service manual.

Make sure you have a good ground.

since it looks like you have the head off, and its leaking w-d 40 when you fill the ports, sounds a lot like a bent valve.
my 2 cents, I would get the head redone this way you know everything is right when you go back this time

Okay let me try to answer these best I can without causing any confusion. Valve job,and barrel clean up was performed by machine shop. I did not replace the valves or springs. only the seals. further conversation with buddy revealed.same piston rings were reused. I'm running bs 34s on it. I didn't have the cylinder bores checked, believed they should be okay. found after turning head over the # 2 cylinder was clean compared to the other three. So do you guys think its better to try the rebuild again, or purchase a running replacement. open to suggestions

roccbottom wrote:

Now after having no compression before getting the cams lined up correctly, set the cams to have the following numbers from the cylinders,#1-120 #2-100 #3-140 #4-150. added the cap full of oil,compression didn't change.

You added a cap full of oil through every spark plug hole and didn't get a increase in compression??
That's crazy! Almost 50 years of turning wrenches and I've never seen such a thing. Four cylinders with oil added and none came up in compression?? Go get another Compression tester.

A bench sync only gives you a starting point for a vacuum sync on the bike.

BS34's? I'd physically check the throttle blades to see if they are actually wide open when the throttle is.

steell wrote:

roccbottom wrote:

Now after having no compression before getting the cams lined up correctly, set the cams to have the following numbers from the cylinders,#1-120 #2-100 #3-140 #4-150. added the cap full of oil,compression didn't change.

You added a cap full of oil through every spark plug hole and didn't get a increase in compression??
That's crazy! Almost 50 years of turning wrenches and I've never seen such a thing. Four cylinders with oil added and none came up in compression?? Go get another Compression tester.

A bench sync only gives you a starting point for a vacuum sync on the bike.

BS34's? I'd physically check the throttle blades to see if they are actually wide open when the throttle is.

I assume he added oil to the low reading clyinder, not all 4.....but hey...ya never know. But, be that as it may, if it's a valve problem the oil isn't going to raise compression anyway.

fill ports with solvent and blow compressed air around edge of valve and seat on each cylinder and look for bubbles in port,flip head over and repeat on other ports

Man thats funny right there I dont care who you are. no just the # 2 cylinder didnt rise. accept my apology for not specifying which cylinder it was.I know it can be a pain,when you try to help,but only have partial information.After talking to you guys.I most likely will start rebuilding it after the parts arrive, so I wont have the same problems occur. should I have the head redone. or just replace all the other parts in the head?

roccbottom wrote:

Man thats funny right there I dont care who you are. no just the # 2 cylinder didnt rise. accept my apology for not specifying which cylinder it was.I know it can be a pain,when you try to help,but only have partial information.After talking to you guys.I most likely will start rebuilding it after the parts arrive, so I wont have the same problems occur. should I have the head redone. or just replace all the other parts in the head?

If you can take the head apart yourself, here's what to do.

Remove the old valves. Clean the valve seats up with brakeclean.

Clean the new valves with brakeclean.

Take a blackmagic marker and paint the 45 cut on the valve with it.

Before it dries, poke the valve down in the guide and seat it. [use a lapping stick]. DO NOT SPIN IT!

Pull the valve out and inspect how the marker transferred to the seat. If it's a perfect seat, the marker should stick and you should see a nice black line all the way around the seat.

Post pictures if you can. Hard to analyze what you can't see...

larrycavan wrote:

roccbottom wrote:

Man thats funny right there I dont care who you are. no just the # 2 cylinder didnt rise. accept my apology for not specifying which cylinder it was.I know it can be a pain,when you try to help,but only have partial information.After talking to you guys.I most likely will start rebuilding it after the parts arrive, so I wont have the same problems occur. should I have the head redone. or just replace all the other parts in the head?

If you can take the head apart yourself, here's what to do.

Remove the old valves. Clean the valve seats up with brakeclean.

Clean the new valves with brakeclean.

Take a blackmagic marker and paint the 45 cut on the valve with it.

Before it dries, poke the valve down in the guide and seat it. [use a lapping stick]. DO NOT SPIN IT!

Pull the valve out and inspect how the marker transferred to the seat. If it's a perfect seat, the marker should stick and you should see a nice black line all the way around the seat.

Post pictures if you can. Hard to analyze what you can't see...

Larry works as a motorcycle psychologist/therapist,hes always got a kz motor laying on his bench/couch talking about its traumatic childhood at the hands of some speed freak! :woohoo: