1972 Kawasaki 500 H1B

[JackyJoll]

In the early 70s, you had to have big cowhorn bars, although nobody knew why.

[rodbargee]

Looks Fantastic!

[Skub]

I was out the other day on the H1b and it was going well as it always does. I filled up with fuel after about 100 miles and headed home. When I pulled into the driveway the bike idled as usual,just under 1.5k,then it began to stumble down to 1k and below and back up again,eventually it stalled.

The bike pulled fine from all rpm,no missing or flat spots anywhere,just the stumbling idle. I changed the plugs to rule out simple things first,but made no difference.

In a process of elimination,yesterday I replaced the three HT leads. Upon firing the bike up.it became obvious the issue remained. One item in a process of elimination down.

After I came back from a test run,I set the bike on the sidestand and had myself a think. During the thinking I became aware I could smell petrol. Sure enough,there it was pissing from the overflow of the r/h carb. I took the carb off expecting another dodgy float,but nope,the float floated just fine with no rattle inside either. I gave everything a good blowout and all the tiny holes and passageways were free and clean as a whistle.

Rather than use the float height measurement,I like to set the fuel level. When the fuel level reached 4mm it kept on going until I turned off the fuel. So long story short I reset the fuel level,synced the carbs again,put it all back together and crossed my fingers before starting.

Let the bike warm up and it idled nicely. Took it for a short 20 mile run with lots of stopping at junctions and the idle remained steady.

As to the cause of the fuel height changing,I can only assume that everything gradually goes out of tune over a period,but you don't notice until normal running is affected. What seemed like a sudden problem is likely a gradual process. Also,the old maxim of '75% of electrical problems are carburettor related',rings true.

I stink of petrol. Again.

[David]

Better smell than Brut.....

[JackyJoll]

Pour yerself a big ‘andful!

[Ian]

Check the float needles - I've had ethanol cause corrosion under the viton tip which made the tip lumpy so it didn't seal and caused flooding. Looked fine at a glance but close examination revealed corrosion under the ends

[Skub]

Update of sorts.

The rough idle issue remains.

After yesterday's ride,the misfire began to get worse and I've also discovered when I switch on the indicators,the idle falls in time with the flasher unit. So I disconnected the flasher unit and left bar switch to see if it was a problem even when not in use,but the rough idle remains.

I've also discovered it has the wrong battery,rated 7amp instead of 9amp. In a fit of hopefulness I swopped out the battery for the correct one on the H1a. No change.

So far I have..

Tried a proper battery.
Replaced all three HT leads.
Checked and reset carbs.
Changed plugs.
Checked the non resistor plug caps. They read virtually zero.
Visually checked wires and connections for anything obvious.

Maybe a coil breaking down? Whatever it is appears to be getting worse.

I'm done for today,the adventure will keep for another day.

[Taipan]

I'd be looking at the coil, normally the primary circuit. You used to be able to test the coils with a DVM if you had the specs from the manual. One thing though, I had this sort of misfire on a XT660 and the coil was within spec but for the life of me couldn't find anything else wrong with it? In desperation I bought a 2nd hand one off a guy who was breaking a damaged Xt and it cured it, so the meter readings might not show the full picture? Could you swap the coils over to see if the problem follows the coil so to speak?

[Rockburner]

Jota bars dropped or clip ons made my B a lot better.

It's my humble opinion that Jota* bars make any bike better.


* IIRC they were also known as "Tomaselli adjustables" ?

[Skub]

I'd be looking at the coil, normally the primary circuit. You used to be able to test the coils with a DVM if you had the specs from the manual. One thing though, I had this sort of misfire on a XT660 and the coil was within spec but for the life of me couldn't find anything else wrong with it? In desperation I bought a 2nd hand one off a guy who was breaking a damaged Xt and it cured it, so the meter readings might not show the full picture? Could you swap the coils over to see if the problem follows the coil so to speak?

Yeah,static readings from a coil often don't show the real picture,because as things heat up in operation,then a fault can occur.

[Ian]

I'd be looking at the coil, normally the primary circuit. You used to be able to test the coils with a DVM if you had the specs from the manual. One thing though, I had this sort of misfire on a XT660 and the coil was within spec but for the life of me couldn't find anything else wrong with it? In desperation I bought a 2nd hand one off a guy who was breaking a damaged Xt and it cured it, so the meter readings might not show the full picture? Could you swap the coils over to see if the problem follows the coil so to speak?

Yeah,static readings from a coil often don't show the real picture,because as things heat up in operation,then a fault can occur.

The best way to test coil performance is to reach down with wet gloves and try adjusting the plug cap. If you wind up in a hedge like I did you know it's working

[Skub]

The best way to test coil performance is to reach down with wet gloves and try adjusting the plug cap. If you wind up in a hedge like I did you know it's working

Yes,I've even resorted to that. I'd have been happy to get buzzed to find a solution.

[Mr. Dazzle]

Multimeters also don't really work all that well for measuring coil resistance. They just can't put the juice through. The tiny voltage from a multimeter might not expose a faulty coil but the "real" power might.

This is why when you do any serious electrical testing you have to use kit and measurement which is putting the proper loads through stuff.

[Lutin]

I know that you'll have probably already covered this, but are all the earth points clean and making good contact?

[Ian]

Good call Lutin! Later H1s have an extra earth lead from the engine case to the frame (which always gets lost). Try tucking a wire under a cover screw and connect the other end to a good earth and see if tickover improves.

I know later H1s had rubber bush engine mounts but the contact through the engine mounts isn't great on a B with solid mounts.

[Skub]

Cheers fellas.
Earthing seems good everywhere,I even cleaned up the already clean main earth point. It rings out everywhere metal that isn't painted.

I'm going to pull the carbs off again,in case I'm chasing a fuel and an electrical fault and thinking it's all the one fault. The way it's starting from cold on one cylinder before the other two join the party,reminds me of a fuel issue.

The bike came with a cheap shit fuel tap,so I changed it for a good original one,but no difference. Ruled that out anyway.

I'm gonna ride some and leave it alone,before I'm tempted to call on the services of KFB.

[ChrisW]

IN case it's of any interest:

[Skub]

IN case it's of any interest:

I watched that one a while back. I actually left a comment on the video at the time. That bike is really poorly set up,the carbs are off a mile and a mix of thrashing/normal riding will see you in the 40s mpg. The poor mpg and no low down power are all symptoms of bad setup.Plus those pod filters are shite too. It's a pity because it make the vid unrepresentative of the bike. The brakes are shite though...

Back to my own woes.

When the poor running first began to manifested itself,it was about 5 miles after filling up with E5 at a BP station I use a lot. I've drained the tank and carbs and will fill with fresh fuel from somewhere else to see if anything changes. Clutching at straws now.

[Skub]

I stuck in fresh fuel today and took the bike for a short run. Same issue.

It pulls cleanly for the first couple of miles,then begins to misfire badly. Turning on the indicators makes the misfire much more violent.

The header of the middle cylinder is noticeably cooler to the touch,so this is the one being affected. How this ties in with the indicators beats me!

Still,at least I now know it wasn't bad fuel. That's got to be some kind of progress,right?

[mangocrazy]

This is quite possibly me mis-remembering something from my yoof, but problems occurring once the motor is warm/hot could be down to a duff condenser, especially on old bikes with points ignition. Now I know yours has CDI, but does it also run a condenser (I really don't know).

If turning the indicators on makes the misfire worse, what happens when you turn the lights on? It sounds like some part of the middle cylinder electrical system is tracking to earth, even if only to a small degree.

Agree about the Mach III vid, I switched off half way through because he was annoying me and seemed pretty clueless. The bike clearly wasn't set up right and he wasn't smart enough to realise that.