KH100 Bucket Racer - Won't Start!

Bought a 1980 KH100-G7 (according to the frame. motor is stamped G5E) with the intention of racing it as a bucket racer. The previous owner raced it but it sat in the shed since 2006. I'm having a couple of problems with it and its been a pain in the arse to troubleshoot without a kickstarter



Anyways, I'm having problems getting it started again. Managed to bump start it a couple of times when we first got it, but then it became harder and harder to do and now it just will not start. It sounds like the engine doesn't want to fire.

- I checked the spark plug and they were fine, just wet, I replaced them with a spare I had. After replacing them the engine fired a couple of times but would not start, until again, it just refused to fire at all.
- I cleaned the carbys thoroughly, but now its overfilling and pissing out petrol, I know this has to do with the float bowl. Btw the carby is a Keihin PE, I'm pretty sure this is an aftermarket part.
- I opened up the top end (previous owner did a reverse barrel conversion and changed exhaust to suit) to look at the piston and it looks like its missing a piston ring. Would this explain everything that's going on? I've ordered a piston kit and service manual, just waiting on delievery, might take a while to get to Australia from the UK though.

How would I run a compression check without the kick starter? Just plug it in and roll the bike forward a couple of times?

Thanks in advance for any help.

Is it missing the bottom ring? If so it is probably intentional as they give a bit more power with a single ring, but it would be so marginal that I would put em both back in.

is it a total loss system? try to fully charge the battery then go again, It's not uncommon for Buckets to run total loss (it's probably more unusual not to)

Get you back wheel off the ground a bit more (stand is made for 17" wheels so don't help having an 18 with a big profile) so you can spin the back wheel by hand .
Then get your plug out and see if you have spark . Might need a mate to hold the plug to earth .
Take a bit of care that you don't have a gut full of fuel down in the cases and blow it out over a nicely sparking plug Its been done

If you have a nice spark , then you could just be flooded . That carb is definitly an add on and looks quite big .

Looks like fun .

Send Slow and Wobbly a PM and ask him . If he doesn't bite your head off , he might actually help you . Tell him Billy says he knows Jack Shit about Buckets

- Yeah its the bottom ring, unfortunately I don't have the 2nd ring, if that's the case then that might not be the problem then.
- It looks like a total loss system (sorry, not entirely familiar with them). The bike is not running a battery, looks like just the ignition, so I'm guessing it is.
- Lol! I was actually close to sparking a nice trickle of petrol down the frame rails, lucky I noticed it before anything happened! Anyways, the bike is getting good strong, consistent spark. It may well just be flooded. Any tips on solving this? I've never tuned a carby before.

Thanks for all the help so far, much appreciated.

Will send Slow and Wobbly a pm and hope for the best

Last edited by tele22 on Thu Jul 14, 2011 8:39 pm, edited 1 time in total.

Get you back wheel off the ground a bit more (stand is made for 17" wheels so don't help having an 18 with a big profile) so you can spin the back wheel by hand .
Then get your plug out and see if you have spark . Might need a mate to hold the plug to earth .
Take a bit of care that you don't have a gut full of fuel down in the cases and blow it out over a nicely sparking plug Its been done

If you have a nice spark , then you could just be flooded . That carb is definitly an add on and looks quite big .

Looks like fun .

Send Slow and Wobbly a PM and ask him . If he doesn't bite your head off , he might actually help you . Tell him Billy says he knows Jack Shit about Buckets

Might be safer and wiser to PM The GOS

If you don't have a battery it's not total loss
ignore my comments

Get you back wheel off the ground a bit more (stand is made for 17" wheels so don't help having an 18 with a big profile) so you can spin the back wheel by hand .
Then get your plug out and see if you have spark . Might need a mate to hold the plug to earth .
Take a bit of care that you don't have a gut full of fuel down in the cases and blow it out over a nicely sparking plug Its been done

If you have a nice spark , then you could just be flooded . That carb is definitly an add on and looks quite big .

Looks like fun .

Send Slow and Wobbly a PM and ask him . If he doesn't bite your head off , he might actually help you . Tell him Billy says he knows Jack Shit about Buckets

Might be safer and wiser to PM The GOS

I don't bite ! but Ado does know his way around buckets ........

that carbie does look pretty h-u-g-e for a little 100cc donk......and I hope old mate got all the porting right with the reverse-cylinder mod - it has been done before and can work OK.....

You shouldn't need a battery for these motors, they just use a magneto ignition.....as soon as the motor is turning, you should have spark.

If you don't get any response from Slow & Wobbly, sing out. These bikes are a piece of piss - in the meantime, follow everything Billy has said, he has R30 on his cornflakes !!

Ok what you need is FIRE.
Lots of it.
Build a big one and then with all your strength and a mighty banshee scream pick that abortion up and hurl it for all your worth at the bright yellow flames.

There fixed.....
Anything else?

Seriously though that looks like a 24mm roundslide. KH175? Hard to tell.
What you need is a 28mm flat slide Mikuni. Legal for the buckets. You also need a selection of jets.
The problem you have is that all of the standard variables have been removed and it is hard to say what has been done to the internals of that engine. If the previous tightarse only removed the lower ring insted of stumping up for a hone and matched Yamaha J100 piston (go Kart) then I assume the rest has been done half arsed as well.
Head to a wreckers and pick up a KE KH 100 engine in standard trim if possible as the previous monkey has no doubt taken to the rotary disc with a hacksaw and the ports with bastard file.
These engines only ever came with 9hp at the crank and a 19mm roundslide carb. A well set up 100 engine can put out 26hp and run a 28mm flatslide.....how you get there is up to google.....please dont ask me...again. My therapist is now driving an M3 and I'm not.

if the carb is pooring fuel out of it your float level is to high or needle and seat is buggered.also check the main bearings if its sat for so long they can seize and ark out the mag/alternater i had it happen with my 78rm125.

Guessing this thing runs a KX80 ignition if not a Motoplat. Invalid.
Problem is jetting.
A difference of 2deg ambient is enough to cause trouble when running a larger volume carb on an engine that may or may not have been hacked at to flow more fuel and air.
From your description above that with a new plug it would run.....until it got overcome with a too rich mixture. Jetting.

There. I helped.
Now go and build a big fire and dust your hands off with satisfaction.

There. I helped.
Now go and build a big fire and dust your hands off with satisfaction.

Well done Wobbles , that didn't hurt a bit now , did it . ???

Please note the refrain from using this ( ) in the above text .