Bad Starting - Time to bight the Bullet

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Cexley
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Posts: 75
Joined: Wed Oct 14, 2009 4:40 pm
Location: East Sussex

Bad Starting - Time to bight the Bullet

Post by Cexley » Wed Oct 10, 2018 1:44 pm

Ok, lets face it, it's embarrassing. I've finally had enough of my KR's bad starting (and so has my neighbour) not to mention my dented ego.

The usual ritual of bump starting it to get it to reluctantly fire up on the rear cylinder, followed by various further antics to persuade the front cylinder to join in with its back to back neighbour is now an unacceptable pain in my KR-Arse.

The final straw was when it happened to me earlier this week when I dared to let the old girl cool down for 10 mins whilst I quickly downed a mug of tea at my favourite café on my favourite long 3 counties ride out. Enough is enough, it's time to resolve this traditional KR 'quirk' once and for all!

I've now ordered the clutch side gaskets from Gasket Guru and spent several hours studying the manual, the parts diagram and Tim's section on KR250.org covering the notorious KR Tandem's reluctance to start and I've now worked out just how this anomaly occurs. Hopefully, I am correct and will report back once I have stripped things down and made the necessary adjustments to persuade the front and rear cylinders that they are actually part of the same engine!

In a nut shell, the theory/logic goes like this. The alternator is driven from the front crank, but unlike 'normal engines' there is a separate stator with the 2 x CDI pick ups mounted on a separate stator that is driven by the rear crank. As both cranks are interlinked by the clutch on the right hand side, any misalignment or synch error between the two crankshafts will result in the front cylinder's ignition timing being incorrect as the ignition pick up is on the rear crank mounted stator. If this oddball piece of design is the root cause, then Tim's advisory on adjusting the shims on each crankshafts shock absorber pinion should bring the front piston's static advance timing position back into tolerance for it to work with it's dedicated ignition pickup mounted on the rear crank.

The only thing that doesn't make sense is why the front cylinder chooses to work at all and why, once hot, the thing runs fine. I can only assume the mismatch results in the static timing being too retarded to fire up the front pot when all the various parts are cool. However, once things have meshed, oil filled in the various tolerances and all the various key parts in the game have heated up, the ignition timing on the front pot somehow comes back into tolerance when it then reluctantly joins the tandem party.

I'll be back. In the meantime, any additional theories/solutions welcomed.
KR250 Tandem - Love It
KR1 Project - Sold
XT600Z 3AJ Tenere Overlander
TZR250R 3MA Reverse Cylinder - Sold
TZR250R 3XV V-Twin - Road & Track
TDR250 - Road & Track
XTZ850 Super Ten Dakar Sonauto Rep - Sold

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StrokerBoy
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Re: Bad Starting - Time to bight the Bullet

Post by StrokerBoy » Thu Oct 11, 2018 4:17 pm

When I spoke to KR owners in Japan, they all agreed that it fixed or at least significantly improved things. Good luck!
Kawasaki KR250 Tandem Twin (x4) & KS-II 80,
Yamaha RD350LC,
Suzuki GSX-R750RK & RB50 Gag.

podman
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Re: Bad Starting - Time to bight the Bullet

Post by podman » Thu Oct 11, 2018 7:54 pm

Not a KR I appreciate but my LC required to be bump started after being sat for a very short period of time a couple of years back, the cause for that was two fold.

Firstly the fuel tap "letting go" and allowing fuel into the carbs and the carb float valves not stopping the fuel flow , a replacement tap and carb clean/adjustment got me back to just being able to kickstart it again!

Cexley
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Posts: 75
Joined: Wed Oct 14, 2009 4:40 pm
Location: East Sussex

Re: Bad Starting - Time to bight the Bullet

Post by Cexley » Fri Oct 12, 2018 8:01 am

Hi Podman. Yes, all good calls. In fact, the first thing I looked at on day 1 was for a sticking float or blockage in the front carb. I also discovered the foam air filter had disintegrated and been sucked into by both carb's, so yes, I had the whole lot apart, cleaned, set the float heights and fuel levels as per factory manual.

It has run spot on since, yet the front pot's cold starting (or even 'warm' starting) persists, so now I'm in the weird and wonderful territory of exploring KR pecific design quirks.

I wish it was a 'normal' fueling or ignition problem (not to mention disk valves...), but I'll go with Tim's Jap twin crank synchronisation theory to at least eliminate it from the enquiry!

As soon as the gaskets turn up, I'll get onto it and take a few pics along the way to share with any fellow sufferers out there.
KR250 Tandem - Love It
KR1 Project - Sold
XT600Z 3AJ Tenere Overlander
TZR250R 3MA Reverse Cylinder - Sold
TZR250R 3XV V-Twin - Road & Track
TDR250 - Road & Track
XTZ850 Super Ten Dakar Sonauto Rep - Sold

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