Bad Starting - Time to bight the Bullet

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Cexley
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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.
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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!
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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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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
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Cexley
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Re: Bad Starting - Time to bight the Bullet

Post by Cexley » Fri Oct 26, 2018 6:38 pm

Hi all. Well I’m just back from a week away and put today aside to begin the KR crank synch challenge. It s a 2 stage process to get to the crank pinions. Stage 1 is to remove the clutch cover and the clutch ‘pack’. This smacks of race bred technology as all that holds it on is a circlip. Very neat. There are then 3 holes in the back of the clutch basket, which 3 bolts screw into to act as an extractor to press it off the clutch shaft splines. All very nice and well thought out design by Kawasaki, until STAGE 2!....

How the hell does the inner clutch cover come off?!

The manual offers no help or tips on getting it off to reveal the crank pinions, disk valves etc, just ‘remove cover’.. in the instructions and no mention of special tools etc.

I can see there are 3 bearings in the case. One for the clutch main shaft and one each for the 2 all important crankshaft pinions, so do the inner cover and bearings combine as a pressed fit?..

No amount of gentle tapping, levering or wriggling will remove the cover, so is there a special extractor and/or technique to remove the cover?

I’ve called a halt to proceedings as I’m now definitely in ‘this could go horribly wrong’ territory!

Hopefully someone out there has had the inner clutch cover off and can advise?
KR250 Tandem - Love It
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TZR250R 3MA Reverse Cylinder - Sold
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Skyeport
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Re: Bad Starting - Time to bight the Bullet

Post by Skyeport » Sat Oct 27, 2018 12:33 pm

Hi Cexley, Just had a look at my dismantled end. I don't remember any special way to remove the cover, pretty sure it was just make sure all boltsa are removed then a bit of gentle persuasion.
I tried to insert a photo I have of the cover & case off but didn't seem to upload. Will try again.

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Re: Bad Starting - Time to bight the Bullet

Post by Skyeport » Sat Oct 27, 2018 12:33 pm

Hi Cexley, Just had a look at my dismantled end. I don't remember any special way to remove the cover, pretty sure it was just make sure all bolts are removed then a bit of gentle persuasion.
I tried to insert a photo I have of the cover & case off but didn't seem to upload. Will try again.

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Re: Bad Starting - Time to bight the Bullet

Post by Cexley » Wed Oct 31, 2018 3:31 pm

Hi Skyeport,

Thanks for the advice. I was concerned any further force or 'persuasion' might end up with a cracked clutch cover or worse.

Meanwhile, I have been corresponding with Ted Sagar from New Zealand who races his heavily modified and tuned KR250 in a classic production class race series. He is very knowledgeable about all their quirks and habits and is fairly certain the poor starting is almost certainly carburation and that the crank pinion synch and ignition timing are very unlikely causes of the bad starting, so... before I wreck my clutch and crank cases, I though I'd revisit the carbs and do a full forensic exercise on them.

Well, guess what, there is gallery in the base of the float bowl with a small hole by the drain screw that allows fuel through an imbedded brass jet that then goes up a gallery in the side wall of the float bowl to the choke mechanism in the main TM28SS flat slide's carb body. The tiny imbedded brass jet in the bottom of the float bowl was blocked up with solid crystallised ethanol deposits. It took over an hour in the ultra sonic bath and some serious blasting with an airline to clear it.

I have yet to put it all back together to see if this was the root cause of the bad starting on the front pot, but its stacks up that the fuel flow to the choke was blocked which explains why the rear pot starts up (the carb sits higher and doesn't seem to have built up any deposits in the float bowl) and the front pot only reluctantly chimes in as the heat from the engine and coolant from the rear cylinder circulates to warm up the front cylinder.

I wonder is this has been the root cause of this common problem all along? I suggest anyone with cold start problems also checks out the fuel feed in the base of their TN28SS carbs as well.

I'll report back once all is back together. Hopefully we have collectively nailed it!
KR250 Tandem - Love It
KR1 Project - Sold
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TZR250R 3MA Reverse Cylinder - Sold
TZR250R 3XV V-Twin - Road & Track
TDR250 - Road & Track
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StrokerBoy
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Re: Bad Starting - Time to bight the Bullet

Post by StrokerBoy » Thu Nov 01, 2018 1:24 pm

I hope you've fixed it. :P

My own personal unscientific opinion is that any tiny deviation from 100% new and standard (dirt in carbs, degraded coil wiring, slop in timing gears, stale fuel, etc etc) contributes to the poor starting, so every tiny improvement in one area is a step in the right direction. These bikes just seem more susceptible to things being slightly off than most, possibly because they're over-complicated.
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Cexley
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Re: Bad Starting - Time to bight the Bullet

Post by Cexley » Tue Nov 20, 2018 6:15 pm

Well, between Ted Sugar and I, we got to the source of the problem. Although, the parts diagram gives the impression the ignition pick ups sit on the separate crank rotors, the ignition timing inspection caps on the left crankcase covers would confirm otherwise. They each sit on their own respective crank. And yes, Ted was right in saying it is almost certainly carburation.

There is a hidden channel in the base of the float bowl that feeds up through the wall of the float bowl to the choke mechanism. This was totally blocked in the front carb and required several sessions in the ultrasonic cleaner and repeated blasting with the air line before it finally cleared of the dreaded crystalline build up that evaporating and stale ethanol fuel now seems to plague any bike left standing more than a few weeks.

I have also now adopted Ted's recommended KR250 start technique. i.e. fuel on prime, full choke and NO THROTTLE and it fires up first kick. I leave it to idle until both pots have settled down and then slowly back off the choke. He also recommended double checking the free play on both the throttle and choke cables to make sure nothing else is messing the mixture up, as sometimes the choke plungers don't seat properly and screw up the pilot mixture. Everything works fine now and it starts first kick every time! Amazing.
KR250 Tandem - Love It
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XT600Z 3AJ Tenere Overlander
TZR250R 3MA Reverse Cylinder - Sold
TZR250R 3XV V-Twin - Road & Track
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XTZ850 Super Ten Dakar Sonauto Rep - Sold

podman
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Re: Bad Starting - Time to bight the Bullet

Post by podman » Tue Nov 20, 2018 9:25 pm

We do love a happy ending, well done...

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the KR kid
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Re: Bad Starting - Time to bight the Bullet

Post by the KR kid » Tue Nov 20, 2018 9:43 pm

Great result!

I always used to start mine on choke only, as merely looking at the throttle was the kiss of death.
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StrokerBoy
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Re: Bad Starting - Time to bight the Bullet

Post by StrokerBoy » Thu Nov 22, 2018 10:01 pm

Nice one.

I never touch the throttle on mine either, not sure why I never mentioned it, sorry.
Kawasaki KR250 Tandem Twin (x4) & KS-II 80,
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Re: Bad Starting - Time to bight the Bullet

Post by Sweeks » Sat Nov 24, 2018 12:20 am

Hello, I’m new to this forum and to KR’s,
I was very interested to follow this post on the hard starting issue.
It appears that Cexley decided not to follow through with crank damper procedure.
So, I will go ahead and start with mine.
I have removed them and found them to be in need of shims. ( they measured out of spec)
I had already planned to clean the carbs and will address those when I start re-assembly.
My bike (1984 KR250) is hard to start and it came very close to overheating on my first ride.
I removed the left side of the engine; I found a rusted hole in the water pump housing.
I decided to remove the engine and disassemble it to familiarize myself with this design and re-seal it.
I would love to be able to contact Ted (Sugar/Seger)? To see what performance enhancements (porting) he would recommend, while I have it apart.
After setting up the dampers, I understand why it would cause starting issues (timing).
Cexley, please ask Ted if I could contact him.
Thanks,
Shane

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500bernie
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Re: Bad Starting - Time to bight the Bullet

Post by 500bernie » Sat Nov 24, 2018 10:46 am

Does this bring an end to KR owners bump starting their bikes now?
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