idling problems

[MarJayRD]

After having my rear shock rebuilt by brook suspension I recently got my KR1S MOT'd and taxed, and I'm able to ride it. It rides well, corners nicely and the engine has a pleasing zing which none of my bikes have really had since I had a 2MA TZR.

However... Starting it is a total pig. It needs loads of kicks from cold which I kind of understand. It seems to need to be put onto prime for a few seconds before you give it a go. It will often fire and then runs hideously until it's warm, when you can keep it going if you do it all first time. All of this is reasonably expected for an old two stroke, if a little on the difficult side. However the idle is very high, and takes ages to settle. I spent a couple of weekends fiddling with the idle screws, and I tried setting them to the manual setting of 1 and 1/4 turns out from fully in. When I did this, the idle was no slower than 3000rpm and it took ages to settle to this. I can actually reduce the idle with the choke.

If you think it was difficult to start when cold... that's nothing. When hot it won't start for love nor money. You can occasionally get it to fire, and then you have to be quick on the throttle to get it up to the right speed. The most reliable way to start it when hot is actually to let it cool down! This means that it's nearly impossible to ride anywhere on it.

I think I know what the problem is... but I'd like people to confirm. The inlet rubbers are surprisingly flexible, and have some cracking. My guess is that the issue is an air leak on the inlet? This is an exceptional pain as I don't think they are available from Kawasaki any more... Is there any easy way to test this? A suggestion on another forum was to wave an unlit blowtorch around near the rubbers to see if there is a leak, and it didn't seem to have an effect.

video here

https://youtu.be/wo54bHYUuA4

Someone also suggested it might be a bad crank seal... I flipping well hope not.

The inlet rubbers are cracked:




Any ideas?

[500bernie]

New ones still available from Cradley at £32.09 each (16065)
http://www.kawasakioriginalparts.com/ro ... country=GB

Cheers,
Bernie:)

[MarJayRD]

New ones still available from Cradley at £32.09 each (16065)
http://www.kawasakioriginalparts.com/ro ... country=GB

Cheers,
Bernie:)

That is very useful to know, but I guess I need to take the thing apart and see if the inlet rubbers are the issue before shelling out £60.

Anyone know a way I can rule out crank seals?

[jarno]

if you want to test the inletrubbers just spray some brakecleaners on there if the engine react to that the rubbers are not perfect anymore.


also clean the carbs with a ultrasonic cleaner maybee there dirty and that could couse bad starting the engine cold and warm.

[500bernie]

Like Jan says, clean the carbs and synchronise them correctly. Your bad starting sounds like badly adjusted choke cables. Pull the rubber boots off the choke cables and gently pull the outer sleeve (to feel for play before the plunger starts to lift), adjust them both so they both have the same amount of slack.
Good luck
Cheers
Bernie

[JanBros]

main thing is to check both exhausts : do they both "blow" the same ! because each carb has it's seperate idling screw.

next the air screw : what the manual says is rubbish : 1 1/4th out is way too lean. better start somewhere arround half to 3/4th out.

[MarJayRD]

main thing is to check both exhausts : do they both "blow" the same ! because each carb has it's seperate idling screw.

next the air screw : what the manual says is rubbish : 1 1/4th out is way too lean. better start somewhere arround half to 3/4th out.

Both exhausts appear to push out equal gas pressure, and I have been adjusting both idle screws. Why the hell one is on a cable and the other is on a screw on the body of the carb is anyones guess. It makes it very hard to get both to the same setting. I've adjusted nothing except the idle screws, which I assume are the same as on my 350 YPVS in that screwing them in increases the height at which the carb slide sits when the throttle is closed.

[JanBros]

again : check your rubbers with brakecleaner and than set your mixture screws a lot richer.

[Bertie_Mollie]

Try opening your tank filler cap when you are trying to start it. Might be your vent in the fuel cap is blocked. This COULD be one reason for the poor starting cold.

The high idle MIGHT be "hanging" because of too much air. COULD also be poor idle adjustment or both.

Wouldn't be a bad idea from the sound of it to start from scratch.

Generally I disassemble the carbs, removing all jets and air screw and if you can security screws for the "jet holder". Then try to clean them with carb cleaner as best I can (don't have an ultrasonic cleaner) make sure the little jet hole in the float bowl is clear (I usually carefully poke it through with a really fine needle ). In your case might be a good idea to clean and check the operation of the fuel tap.

Then re assemble them with float heights set correctly.

I set the air screws to the manual and then set the carb slide heights the same with the idle adjusters (as a starting point) using vernier (depth bit) from the top of the carb body without the cab lids or cables connected. This gives a starting point where they are both close to the same height.

I then put the tops on and fit the cables and use the carb top adjusters to balance the openings of the slides.

If this starts and runs let it warm up and then see if you can adjust the idle down turning both sides by the same amount to keep the idle synchronised.

If the revs are slow to come down then richen up with the air screw (can't remember which way to turn them)

Finally when I get it better I usually take the cables off again and re balance the slide heights for idle and then re fit cables and re balance the carb opening with top adjusters.

TBH, I generally end up doing this more than a few times as re cleaning is needed.

It is a ball ache but you can get a feel for it after a while to work out what the problem is.

Regarding the carb rubbers, almost all of the ones I have seen have been cracked but I don't think I have ever seem any leak because of splits. Having said this you may be unlucky - LOL.