help-compression and electrics..

R

rich

Active Member
Hi guys my names Rich, gimme a hand if you could,
I've got a few questions and would appreciate any tips..here's the bike http://s1220.photobucket.com/albums/dd442/rich19751/


1-compression- cant get over 75 but can hear a wooshing noise like air escaping the Bike has no tank- exhausts are disconnected and the carbs has no airbox- what do I need to do to get a compression reading? I'm using a spanner to turn the crank on reccomendation but the bastard keeps slipping off is there a better way?


2- electrics- any tips on how to lash up the ignition so I can try to turn her over- or is it better to just wait and do it all the first time.


thanks guys ...
 
That's a KZ750, correct? Have you gotten a service manual for it yet?

With a cold compression of 75psi, either you have a blown piston ring or your valves need adjusted badly. Pour a teaspoon of engine oil into each spark plug hole and try it again. If it stays at 75, it's your valves. I'm clueless about your bike, but I'm guessing it doesn't have a kickstarter?
 
yeah KZ750 shaft 1984.


Thanks for your response, Yeah no kickstarter,


The thing is I can hear the air coming out ..I was thinking that with the carbs open one end and the exhaust dismantled on the other, while the fuel tank and oil leads are sticking out all over the place .I might have to reconnect something to get compression-


the other thing is my turn slip- bang my hand - get a sore back- crank spinning technique might not be generating enough pressure.
Does anyone know ? im hoping its not a blown ring.
 
We all want to help you, but you are sooo far over your head on this project that it isn't easy.

The carburetors and exhaust do not "hold in compression." It is the valves and piston rings that hold in compression. A compression test can be done on an engine that is not connected to anything.

You might try turning the engine over by putting the transmission in 5th gear and turning the rear wheel. You could also connect a battery to the engine case and starter terminal with jumper cables and spin the engine over. Spray some WD-40 into the spark plug holes. Make sure there is some oil in the crankcase, and spin the engine over for 10 seconds. That will get things lubricated. There could be crud in the valves causing them to leak. Just turning it over a few seconds like that might help clear the crud out. Then try your compression test again.

You need to determine where the "whooshing" noise is coming from. It's possible that the cylinders are so dry of oil that the rings wont seal. It might have a blown head gasket.

Google "cylinder leak down test." You should be able to rent a cylinder leak down tester or have a local bike shop do it for you. That will identify where the air is "whooshing."

You didn't really pay $500 for this bike, did you?
 
Alfa is right there.

To do a compression test, all plugs out, throttles should be wide open and the motor has to turn over fairly fast. Brisk push will do it or jumper leads to the starter will work too. The gauge will go up in jumps until it settles after 5 or six full cycles. That's the reading you want.

If it hasn't run a for a long time valves are probably stuck open with rust flakes and the bores will be dry, so will cam bearings etc, so don't over do it.

Id compression is really that low when tested with the right technique, then the top end has to come off for a clean up. It's not hard, but it does take time, some special tools and a clean methodical approach (plus a good manual).
 
<<throttles should be wide open>>

Uh...in this case, no carburetors. <G> You don't get any more wide open than that.
 
Carbs are on but no airbox IIRC. It was also just a reminder to others too. We should start a sticky with some of this stuff

Good point though. With CV carbs, its easier without any carbs with slides getting in the way of the air.
 
AlphaDogChoppers said:
We all want to help you, but you are sooo far over your head on this project that it isn't easy.

lol- gotta start somewhere..over my head was kind of the point -and no the bike ended up being basically free after walking off. less than scrap value and a good chance to learn
I've sent for a manual in the mail but it wont arrive for a while- so I'll restrict the questions as much as possible...hell I'm enjoying myself and I've got a bike that rides already..this is for fun.
Click to expand...
 
AlphaDogChoppers said:
We all want to help you, but you are sooo far over your head on this project that it isn't easy.

lol- gotta start somewhere..over my head was kind of the point -and no the bike ended up being basically free after walking off. less than scrap value and a good chance to learn
I've sent for a manual in the mail but it wont arrive for a while- so I'll restrict the questions as much as possible...hell I'm enjoying myself and I've got a bike that rides already..this is for fun.


The choice is as I see it..buy another bike and have a nice row of machines that I know nothing about and pay mechanics to fix, or get off my ass and work it out with a cheap bike and a few (maybe a lot) of questions.
If I was doing something I was already good at, it wouldn't be a project- I already do things I'm good at.


Anyway- thanks for the advice I do appreciate it, I'm going to try



pushing it in fifth for the other three plugs..if I can find fifth on the somewhat unreliable gears (lol)


trying to work out how to connect the starter up to get her turning over


oil in the plugs to see if its rings


once the manual arrives I'll rip her out and try a top end rebuild
Click to expand...
 
<<bike ended up being basically free after walking off.>>

I'm very happy to hear that. It tells me that you are listening to at least part of what we are telling you. <G>

<<hell I'm enjoying myself ...this is for fun. >>

After all is said and done, that is pretty much the point.

I would encourage you to not be too quick to tear into the engine. It's unlikely that the engine is so fucked up that it won't run. I would suggest that you put the bike together, and get it running. This is what bike builders call "mock up." That's how you determine where everything goes, what is missing, and really get a feel for where you are going with the bike. THEN start tearing it down, paint the frame, polish engine cases, rebuild the engine, (if needed.) It would be a shame to spend the money on engine repairs only to get stymied by the assembly and wiring of the rest of the bike.

Right now, you don't have a plan. You are just wingin' it, but you don't have a lot of the basic mechanical skills and knowledge to just tear into it with any plausible path to success.

Get that baby running and rideable. That will give you a solid success to buoy your efforts onward. THEN, decide on your next step. I know it's not that easy to hear someone tell you that you have bitten off more than you can chew, but take that to heart, and don't keep biting off bigger and bigger bites. No point in choking on the project.
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light
    • www.jadusmotorcycleparts.com
    www.lostapostle.ca/
    www.sparckmoto.com

    Spread the Love

    Back
    Top Bottom