KR-1S.co.uk Forum

what do you mean by rear cylinder?

I would almost certainly say, you'll get it running smoothly with some minor adjustments to your carburetion. Check the air screw adjustment and also what jetting sizes you're running.

I think its a tandem twin ben

Maccas

maccas wrote:I think its a tandem twin ben

Maccas

Yes I see now

Luders wrote:

maccas wrote:I think its a tandem twin ben

Maccas

Yes I see now

This is the Tandem Twin section after all.

I know I know, it just slipped my attention and was thinking of something else

Ok, so it's running a lot better now that I've connected the fuel tap vacume hose. Woops!

The rear cylinder is still smoking a whole lot more than the front though. Like, pumping out the smoke on the rear and, I guess, faily normal levels on the front.

Check the video for an idea of what I'm talking about.

http://youtu.be/-fqL1nZJbns

I tried running premix and disconnecting the oil pump, made no difference. I guess the rear is getting too much fuel?

I swapped the carb's, front to rear, to see if that made a difference. Nope.
A friend suggested that there may be oil built up in the rear crank case. It's sat for about 7 years with oil in the oil tank. Some might have found it's way into the crank case. It seems to be running hapily enough so I'll get it ready to go and take it for a run. See if it burns off.

I think if you give it a good run it will clear that out

If running it for a while doesn't get rid of smoke from my experience with KR motor rebuilds I would suggest it could be sucking gearbox oil into the rear crankcase. Could be a seal replacement (complete motor strip down!) but I have also found the crankshaft main bearings work loose in their housings (due I think to incorrect crank damper setup causing vibration) & the subsequent runout causes oil to get pass seal. I have not tried this but you might be able to check for play in bearings by removing left side cover & see if there is a detectable up/down movement in rotor. How many K's has the bike done?

hi its always worth checking the RH seals that go around the crank dampers 1st before going for the full strip. had the same fault with mine when i stripped. the LH seals were new, but the RH side seals and running surfaces on the dampers were shot

The bike's done a few k's... 70... thousand or so.

No idea of the history though, there's several parts with the telltale white paint marker 'kr250' writen on them, obviously from a wrecker. I couldn't even say if the instrument cluster is original.

I won't worry too much untill I get the brake pads replaced and take it for a ride.

Agree with Dougindoors on checking right damper side seals.
One bike I bought had 40k on the clock and had a seal problem - was blowing smoke like yours in the video!
Other bike had 32k on the clock & had had a catastrophic big end failure.
Both motors had wear in main bearing housings. I was fortunate enough to find a very low k motor in pieces from a wrecker which I used in my current kr frame.
Let us know how you go.

So how do you avoid the case damage from the bearings moving about? Loctite or something like that?

Loctite is fine. Also check the crank is not loose in bearing which I found on one motor (loctite fine for that too).
One set of cases I machined & put steel liners in - a lot of work but at the time I managed a workshop so had all the gear to do it!

StotheH wrote:Ok, so it's running a lot better now that I've connected the fuel tap vacume hose. Woops!

The rear cylinder is still smoking a whole lot more than the front though. Like, pumping out the smoke on the rear and, I guess, faily normal levels on the front.

Check the video for an idea of what I'm talking about.

http://youtu.be/-fqL1nZJbns

I tried running premix and disconnecting the oil pump, made no difference. I guess the rear is getting too much fuel?

I swapped the carb's, front to rear, to see if that made a difference. Nope.
A friend suggested that there may be oil built up in the rear crank case. It's sat for about 7 years with oil in the oil tank. Some might have found it's way into the crank case. It seems to be running hapily enough so I'll get it ready to go and take it for a run. See if it burns off.

Mine does the same but from the front cylinder, not sure why, maybe a build up of crap over the years