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Author Topic: KZ 250 C "Blueberry"  (Read 2895 times)

Offline teazer

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Re: KZ 250 C "Blueberry"
« Reply #20 on: Dec 20, 2017, 10:52:19 »
That mini voltmeter is showing 11.8 which is a little low.  Try charging the battery and see if that help any.

Offline dray

  • Posts: 26
Re: KZ 250 C "Blueberry"
« Reply #21 on: Dec 31, 2017, 09:21:03 »
Howdy all, it's been a busy time, merry Xmas and HNY!
I've been chasing my tail trying to fix the idle issue, 11 days judging by the last time I posted and this is what happened.
Compression - 145psi +, good spark, battery recharged showing 12.8v, Carb jets set to spec, 91 fuel in the bowl, valves adjusted and checked.
I sprayed starter fluid into the carb with the throttle open then turned her over.
The starter motor cranked away like a champion and the engine pumped and popped but every time I took my thumb off the starter button everything died.
In facebook discussions with locals as well as talks with mechanics at my work I had suggestions of timing, carb adjustments/air-fuel mixture issues, flooded. vacuum and blocked jets.
So I decided to go over everything. Re-cleaned the carb for the dozenth time then tried different variations of jet adjustment, adjusted the float bowl to different heights. No improvement.
So I had a look at timing. Off came the Cam shaft cover, as it so happened the sprocket was 15 - 20 degrees clockwise from TDC. Alarm bells rang and I was confident I had found the problem. I took the cam sprocket off, rotated everything back to TOP/TDC, rotated and checked TDC on crank and cam, checked valve gap, rotated again, checked gap, closed it up and fired away. 
Result was ... Worse. A clear pinging sound was now coming from the engine as the inlet valve hit the piston.
Off came the top part of the head, sure enough there was the imprint of the valve left on the piston. I gave everything a quick scrub to remove the carbon then tackled the head.
Removing the rocker pin, I took out the inlet valve and stuck it into my drill. Thankfully it spun even, no bends.
I noticed that even though the TDC mark on the flywheel was lined up, the piston itself still had around 10mm/half inch of travel before it reached TDC.
I made a mental note of this so as not repeat the mistake of rotating the cam too far counter-clockwise.
I took the lower head off, replaced the gasket and seals, slid the piston back in, returned the top head, fitted the cam sprocket and adjusted to be about 10 degrees clockwise of TDC.
Fired it up again, no improvement. The same result kept happening no matter what I was trying. It would fire up, pump away but as soon as I took my finger off that starter button it would die.
This got me thinking about the electrics. More information - I had replaced the handlebar switch blocks with some cheap online ones. The originals had corroded with buttons and switches not working. The new switch blocks worked fine .... except ... the kill switch was inverted.
I had tried all kinds of combinations with the 3 wires that determined the starter switch and kill switch function and the only way to have it perform close to standard format was in this inverted set up. The inversion itself was a physical thing where the red button would only bridge the two wires by clicking up instead of down.
I hope this makes sense.
In any case I had exhausted all the mechanical options I could think of so I decided to hook up the original switch which still had functioning kill switch and starter.
Yup, you guessed it. The bike started and purred like a new born kitten...

Offline Popeye SXM

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Re: KZ 250 C "Blueberry"
« Reply #22 on: Dec 31, 2017, 13:47:41 »
Well done. Don't you hate it when you are doing it ''by the book'' and still getting it wrong. I hope things go a little easier from now on. Have a good new year

Offline Pete12

  • Posts: 138
Re: KZ 250 C "Blueberry"
« Reply #23 on: Jan 02, 2018, 19:39:43 »
Good job getting it running but you might want to check the rotor key as it must have sheared to have the TDC mark in the incorrect position in relation to the piston position.

Offline dray

  • Posts: 26
Re: KZ 250 C "Blueberry"
« Reply #24 on: Jan 03, 2018, 11:06:05 »
Very interesting you mention this! As shown in the photos above when i pulled the camshaft sprocket cover off it showed what looked like advanced cam timing, as previously mentioned I reset the sprocket to Top as per manual (see photo below) however, all of this is wrong or at least deceiving. Call it a weird design but the Timing mark on the flywheel is reliable for ignition timing only! That and perhaps valve clearance adjustment.
As you can see in the photos above, the piston sits at TDC according to the green timing mark however it still has about half an inch more of travel to reach true TDC.
By the time the piston has reached true TDC, the timing projections on the flywheel had already gone passed the pick up. This must be by design in order to insure complete burn.
All this had me confused and chasing my tail, i had the head off, the flywheel off, replacing gaskets and seals, adjusting valves and sprocket, rotating crank and cam to get a feel of the timing progression.
I dremeled a mark on the flywheel for true TDC and sure enough when that mark lines up so does the mark on the camshaft sprocket  with top.
I hope that makes sense.
« Last Edit: Jan 03, 2018, 11:08:31 by dray »

Offline Pete12

  • Posts: 138
Re: KZ 250 C "Blueberry"
« Reply #25 on: Jan 03, 2018, 17:30:52 »
What you say makes perfect sense but if the flywheel key is intact then it may be the wrong flywheel (or sidecover perhaps) for your model - hopefully a forum member with an intricate knowledge of 250 Kawasaki's will chime in. Regardless, you have done a good job of solving your problem.

Offline dray

  • Posts: 26
Re: KZ 250 C "Blueberry"
« Reply #26 on: Jan 13, 2018, 10:50:53 »
Now the final stages of completing the build are at hand. I've spent time on lots of small jobs i.e dremeling out a mount point for the voltmeter for external display on underseat electrics tray, fabricating rear mount point for seat and torquing nuts to name a few.
I have still to make a rear mount to position the tail light. I can't really do this until the rear fender is fixed in place.
The big job at the moment is getting creative with the paint job. When used right, shiny pearl colours are my favourite finish and that's exactly the direction I'm going with this bike.
I picked up the 2 pack paint last week and have begun the patient process of layering and curing. below are photos of stages 1 - 3. Two more stages remain for the final result.

Offline dray

  • Posts: 26
Re: KZ 250 C "Blueberry"
« Reply #27 on: Jan 13, 2018, 11:08:11 »
In between spraying I've begun the task of tuning the carb.
It's a Keihin pw 26, stock jets include pilot #35, main #105. I have a spare #38 and a #120 to trial with.
 I'll be the first to admit I've got little experience but I've been doing my research and done a lot of trial and error.
Knowing that with the replacement of the stock muffler and air box, the engine would run a lot leaner I thought of introducing a 5k ohm resistor cap would be beneficial. At this point it seems a mistake though I have limited jets to try out.
With the 5k cap it runs very rich and doesn't need choke from cold start. I'm able to turn the air screw all the way out and it has no effect or cause for stumbling.
I've played with the float level and tried various counts of turns for the pilot and air screw but I'm thinking that with the 5k ohm the burn just isn't enough.
Today I replaced the cap with a standard one and there was quite a difference. instead of the mild purring I usually got the bike popped and crackled very loudly. I'm guessing it's on the other spectrum and running lean though when i check the plug it still looks a bit foul.

Offline dray

  • Posts: 26
Re: KZ 250 C "Blueberry"
« Reply #28 on: Jan 20, 2018, 21:12:58 »
Stages 4 and 5 of the paint work are now complete. the blue candy pearl turned out a lot lighter than I had hoped. I think this is due to not only its shade but also spraying silver too thickly. I should have thinned it more and sprayed lightly, with the summer here i think the paint flashes too quick, not allowing me to marblize easily.
End result was not too bad in any case, it has a Miami Vice tone to it.
The stripes i think look good but there's a few inperfections. I'm not 100% sure but the guy who prepared and sold me the paint may have done a dirty trick. Disappointing considering how expensive 2 pack paint it.
To explain. When I sprayed on the silver and black, it was nice and thick and coated well.
I clear coated it all, line taped and masked. I used a custom made vinyl stencil and when all was ready I applied the gold yellow.
The guy at the shop told me 1 part paint 1 part thinner. This worked fine for the black and silver.
When I sprayed the yellow gold, disaster!
It ran and orange peeled, lumping together. I thought maybe I hadn't stirred and strained it properly but when I added more paint (no thinner) to the mix it improved greatly.
The same happened with the white and I'm sad to say that i think the mix had too much thinner that it attacked the adhesion of the line tape and the vinyl started to wrinkle.
So I was a bit devastated and spent some time trying to tidy and rectify but I think the damage was done.

At this point I think the only way to fix would be to sand back the top clear coat. wipe off the stripes with thinner and re stencil. Not a job I'm in a hurry for.

It looks good from a distance  ;D
If any pros out there have tips or procedure on how to fix paint lines I'd really appreciate it.

Offline dray

  • Posts: 26
Re: KZ 250 C "Blueberry"
« Reply #29 on: Jan 23, 2018, 23:47:07 »
So here it is, the final product below. There are some adjustments to be made with the carburetor and a new neutral switch needs to be installed but more on that later. I'm quite proud of the end result as my first rebuild. It's unrefined and rough in a few places but it polished up nicely.
Building a bike was hard, heaps of learning, sometimes torturous when trying to be self taught. It was much more expensive than I predicted but when you fix something where do you stop?
The bike is now getting looked over by these guys https://www.retromoto.co/  before being send to an inspection station to be registered.

Next project: SR 250 scrambler!
« Last Edit: Jan 27, 2018, 09:49:34 by dray »