Normal behaviour for a little KH100

[KayAitch]

Hello everyone,

First post. A long one. I can't help but waffle :)

About 8 months ago I found a little 1979 KH100EL in a motorcycle 'recyclers' that needed a few bits and pieces and a little bit of work. I went ahead and bought it because it was a nice looking little thing and I've wanted a bike for quite some time and thought this would be an interesting place to start.

Having no prior mechanical knowledge has been fun. So after fixing quite a few things (ignition switch, cables, adjusting brakes, brake levers, battery, cleaning/greasing air filter cleaning the fuel tank/hoses et al) AND getting a mechanic to make sure it was carburetting properly, oil pump was doing the job, the timing was set right and the engine compression was otherwise OK it has been running pretty well.

However, it generally only runs well for maybe 35 minutes before it seems to get hot and starts struggling (acceleration stars to go, rev progression gets a little rough - it basically starts to get slower and grumpy). I try and ride it at varying RPMs as much as possible because I've heard that these little 2 smokers don't like to cruise. My mechanic has told me that 'this is just how they are, they need a rest every 35 minutes or so'. Is this true? It'd be nice to get it to a point where it will last 25 minutes before performance deteriorates or even to a point where I could ride it for say an hour without caring too much :)

There are a couple of other little things that may or may not be related to this performance quirk. The first being that I am having some trouble getting the tank cap to vent properly, blowing air through it with my mouth tells me air can get through but I think it isn't keeping up. To circumvent this, and avoiding fuel flow ceasing and the engine cutting - which has happened, I loosen the tank cap while riding every 5 minutes or so. Does the trick.

I'm fairly certain it is missing a regulator rectifier so I have been charging the 6V system every few days or so. I've heard someone say that not having the rectifier can affect engine performance in some of these types of bikes but I am unsure as to how.

Any help would be greatly appreciated. I'll also be diving in with a full respray of the tank and side covers because there is a little rust on the tank.

Cheers,

D

[FR700]

You still got the karmann ghia ?

[KayAitch]

Despite being a little (a lot) creeped out, yes the Karmann Ghia still sits in my yard.

[FR700]

... santa knows when you've been bad


A quick google search for 1979 kh100el puts your widdle post at the very top




http://www.google.com.au/search?q=19...hrome&ie=UTF-8

here - http://kawasakikhregister.myfastforu...ic.php?p=43609




was that so scary ?

.

[FR700]

... and while I'm at it ... your mechanic is an idiot


can you say partial seizure ?

KH100's are still favoured for bucket class racing here in oz ... rest every half hour ... fuck me

Your own thread tells of you opening the fuel tank cap to 'help' it out. It's running lean amongst whatever else is ailing it.


.

[Twin-shocker]

Originally Posted by KayAitch

Hello everyone,

First post. A long one. I can't help but waffle :)

About 8 months ago I found a little 1979 KH100EL in a motorcycle 'recyclers' that needed a few bits and pieces and a little bit of work. I went ahead and bought it because it was a nice looking little thing and I've wanted a bike for quite some time and thought this would be an interesting place to start.

Having no prior mechanical knowledge has been fun. So after fixing quite a few things (ignition switch, cables, adjusting brakes, brake levers, battery, cleaning/greasing air filter cleaning the fuel tank/hoses et al) AND getting a mechanic to make sure it was carburetting properly, oil pump was doing the job, the timing was set right and the engine compression was otherwise OK it has been running pretty well.

However, it generally only runs well for maybe 35 minutes before it seems to get hot and starts struggling (acceleration stars to go, rev progression gets a little rough - it basically starts to get slower and grumpy). I try and ride it at varying RPMs as much as possible because I've heard that these little 2 smokers don't like to cruise. My mechanic has told me that 'this is just how they are, they need a rest every 35 minutes or so'. Is this true? It'd be nice to get it to a point where it will last 25 minutes before performance deteriorates or even to a point where I could ride it for say an hour without caring too much :)

There are a couple of other little things that may or may not be related to this performance quirk. The first being that I am having some trouble getting the tank cap to vent properly, blowing air through it with my mouth tells me air can get through but I think it isn't keeping up. To circumvent this, and avoiding fuel flow ceasing and the engine cutting - which has happened, I loosen the tank cap while riding every 5 minutes or so. Does the trick.

I'm fairly certain it is missing a regulator rectifier so I have been charging the 6V system every few days or so. I've heard someone say that not having the rectifier can affect engine performance in some of these types of bikes but I am unsure as to how.

Any help would be greatly appreciated. I'll also be diving in with a full respray of the tank and side covers because there is a little rust on the tank.

Cheers,

D

Find a mechanic who knows what they are doing, and ask them to first check points and condensor, clean carb out, and decarbonise exhaust. If the top end of the bike is noisy though it may be partially seized, and this would need to be checked first.

[JeffS77]

my guess is that it is running lean and causing it to overheat..maybe sucking vaccum from some where ? or just jetted too lean ...what you describe does sound like a partial sieze..but I am no expert

I have had a '68 and '69 Kawi F3 175 and those things would run hours on end no problem. (watch Cycles South. those guys ran them all the way to Baja) and my '74 TY175 will do the same. What you are describing is not normal by any means. Something aint right.

[KayAitch]

Ha, not at all. Seems like the humble KH100EL isn't all over the internet then. I can't think why

Originally Posted by FR700

... santa knows when you've been bad


A quick google search for 1979 kh100el puts your widdle post at the very top




http://www.google.com.au/search?q=19...hrome&ie=UTF-8

here - http://kawasakikhregister.myfastforu...ic.php?p=43609




was that so scary ?

.

[KayAitch]

Thanks for all your replies.

Can someone define for me what a partial seizure is? I've come across it a lot while reading about these old bikes but I don't think I've got my head around it apart from the fact it is caused by the engine getting too hot, for whatever reason.

JeffS77: When you say "sucking vacuum" from somewhere are you talking about fuel flow issues or an air leak somewhere else in the system that causes this lean situation? As far as the jetting goes, the same mechanic (who is a nice guy and owns a little Honda 100 2 stroke of similar age but did also sell me the "it's a little engine, they get hot and need a rest" line) did recently tune and clean the carby and seemed to think all was OK there. Do you know where I can get a copy of Cycles South online? I'd love to watch it but I can't get Netflix here in Aus.

Twin-shocker: I guess I'll go and get another opinion somewhere. Same guy checked points (not sure about condensor), carb has been cleaned, the only thing is the exhaust hasn't been decarbonised because I think he said the muffler has been welded on or something at the very tip. When you say noisy top-end what am I listening for? It has been compression tested and it has plenty.

Is there anything a relatively mechanical noob like me can try? I'd like to get my hands dirty provided I don't get too out of my depth.

Cheers

[KayAitch]

After having a good chat with the same mechanic (who seemed to think he never said "they just get tired and need a rest") and taking the head off and shining a torch down the barrel it appears there are a few scores down the cylinder wall and these partial seizures are definitely happening. I can definitely feel the scores with my fingernail. The spark plug is showing no signs of a lean situation, the carby is good, oil pump is good, thus i think it's just too worn out in there, evidenced by the 3 to 4 scores. So I'm going to attempt a top-end rebuild and from what I understand it looks pretty simple.

I've measured the cylinder and it seems it is at the original 49.5mm. Which means in 18,000kms and in 33 years it has never been re-bored, not sure what honing will do to cylinder size (?) so I'm not sure if it has had any attention to the top end at all.

Now I have to find out whether a hone will do the trick with new rings and gaskets or if I need to go the re-bore and buy an oversized piston and rings.

Any advice for a noob? I am yet to take the piston off and I have the hole covered with cloth but I'm keen to get the piston off to take a look / play around. I can't seem to find a 'piston pin puller' in any stores around here and one guy said a hammer/mallet and a bit of care will do the trick. Can anyone give me some pointers here?

I'm quite enjoying getting some experience and I'm looking forward to attempting a tour up to the Flinders once this little thing is up to scratch

[KayAitch]

So this thread died in the ass and in the meantime I've rebuilt the top end. Seems to be showing good signs after 3 short running-in trips - 5-10 minutes, 10-15 minutes and 20 minutes respectively. It was a warmish day for the 20 minute run and I gave it a really good warm up before heading off. Usually it would start showing signs of seizure pretty quickly - the loss of power, the bogging down, the stammering - in these conditions but no signs even with it nowhere near run in. Thanks for the unanimous diagnosis, chaps.

I can't wait to do a decent little ride on the flyer since it is spring down here.

On to the next problem:
Previously I was loosening the tank cap because there is a definite cap venting issue. Any advice on cleaning up those vents in the cap? Pull it apart (if possible) or just spray some WD40 or something down the vent holes and give it a good flush?

Cheers