1979 KZ650 - Baby Steps to a Running Bike

Looking for advice from those who have done it before...

Bought the bike for a project. The Electrical forum here helped me to get proper spark (thanks, guys), but the use of transparent fuel lines proved I wasn't getting enough fuel during cranking, and what there was of it was filthy. Carbs are off and I'm rebuilding them. One at a time they are being disassembled, spending 12 hours+ in a Gunk carb cleaner bucket, brushed with a toothbrush where I can reach, rinsed in warm water, and blown out with compressed air through every orifice I can find. 

Question: Is it worth it to get an ultrasonic cleaner? Some videos I've seen of before and after show they don't look any better than what I got with the dip, which doesn't give me a ton of confidence they are superior in cleaning out the insides any better. I know I also have to watch what I use for a cleaning agent, since some can attack the aluminum. It looks like I'll have to spend $150-$200 for a cleaner with a heater and some cleaning agent. Would I have a use for it beyond the carbs? Beyond the bike? I'd need to justify the cost to the wifey...

Also: while trying to get it to start, I performed compression and leak down tests. For compression, cylinders 1-4 read: 145, 120, 140, and barely over 30psi. So #4 is a dead cylinder.
On the leak down test, I didn't exactly have the motor at TDC. I just rotated it until the pressure in the cylinder started to increase. I would rotate through the cycle a couple of times to try to get accurate/consistent readings. This might not be the superior way of doing it, since I think my loss percentage readings were a little wonky in relation to my compression test results. Cylinder 1, which had the best compression, leaked the most at 65%, mostly through the exhaust. 2 was at 45%, mostly through the rings. 3 was 35%, mostly through the rings. And 4 was at 60%, mostly through the exhaust. So, while I'm sure there's carbon on those exhaust valves, I'm pretty sure those cylinders need attention, too. The odometer reads 28,300. I'll bet that's at least 128,300.

Question: Once I get the carbs as put together/functioning as best I can on the bench, should I put them aside and then go straight to a top-end rebuild? That's where I think I'm headed. Everything needs attention, I'm just trying to only do a little at a time so I don't create a parts farm.

Thanks,
Chris

Has the bike been sitting a while? The ring could just be stuck in the piston groves. While your working on the carbs put some Marvel mystery oil into the cylinders. Let them soak. You may also have a little corrosion on a valve if it had been sitting open a while. If you have a borescope you could look inside to see what’s going on. But the easiest course of action while you are working on the carbs is to try and free up or lubricate a possible stock piston ring.

As far as the ultrasonic cleaner that’s the similar question to asking what is the best oil. Everyone will have their own opinion as to what works best for them. I have never used one so I have no idea how the results are. I have good luck with soaking in Barrymans carb dip, and then spraying and cleaning everything out with brake cleaner.

Poor fuel delivery to the carbs, and what was getting there was dirty?  I would address the inside of the fuel tank while you are at it.  Empty the tank, pull the petcock and check/flush the insides of the tank.  The screen on the petcock is probably full of debris as well.

An ultra sonic cleaner if used properly will make your carbs spotless inside and out including all the small critical passages. DO Not mix components from one carb with components from another. Bench sync them and set the bowl fuel level accurately using the wet method.

135 - 140psi is not to bad as I assume they are cold readings. Probably would equate to 150+ on a warm engine which is how it should be done with the throttle fully open or better still no carbs fitted. . One low cylinder is likely a mis read!/sticky ring / valve and needs checking again.

As Skidmark said, old dirty fuel is pointless trying to use and will mess your efforts with the carbs instantly. 

I would not spend the money on the ultrasonic.  Carb dip works far better for deep cleaning.  The only thing the ultrasonic will do is clean off any oily residue left behind from the carb dip.

I recommend shooting carb dip spray though all the passages and making sure none are blocked.

Regarding the low compression, did you adjust the valves yet?  Chances are fair that #4 has tight valves causing compression loss.  Soaking in MMO is a good call.  Adjust the valves and put some good hard miles on the engine.  Only then will you know the true compression situation.

Thanks for the input. I've put some MMO in the cylinders and in the valley where the cams sit and will let it soak a day or two.
The petcock filter looked clear to me, but while I await parts for the carbs I'll address the tank, which has some surface inside.

wrote:

Thanks for the input. I've put some MMO in the cylinders and in the valley where the cams sit and will let it soak a day or two.
The petcock filter looked clear to me, but while I await parts for the carbs I'll address the tank, which has some surface inside.

Be sure to adjust the valves before trying to start the bike again.  If the valves are hanging open you will just cause more damage by running it further.

Here is a good way to insure a really clean fuel tank.

www.kwick.biz/how-to-flush-your-fuel-tank/

wrote:

Here is a good way to insure a really clean fuel tank.

www.kwick.biz/how-to-flush-your-fuel-tank/

For some reason that link doesn't work for me.
"This site can’t be reached"
 

wrote:

wrote:

Here is a good way to insure a really clean fuel tank.

www.kwick.biz/how-to-flush-your-fuel-tank/

For some reason that link doesn't work for me.
"This site can’t be reached"

 

Weird. It works fine for me. Here is the home page address for that site.
www.kwick.biz

Go to Kwick’s Corner and scroll down a bit.

Thanks.  That link works now. Maybe it was down briefly.

wrote:

Thanks.  That link works now. Maybe it was down briefly.

Solar flares? Global warming? Midget zombie apocalypse?