Jetting for top-end rebuild

[Dandb7]

Hi to everyone,

Can anyone help on my jetting issue..? I'm running stock Keihin's and just got the top-end rebuilt...again...

Initially, i had a ''cold seizure'' on my mag side piston/ring and had to get the cylinder nickasiled + piston changed....so thinking i would do right i got both cylinders done and changed both pistons (bought from Bob at image)...to be on the safe side..!

On my first run with the refreshed top end (this was last march), did the usual warm-up(till heat exchanger got warm), varied throttle quite a bit without going all out of course and when got to a nice opening in the field, kept throttle about halfway for about 10 seconds.....and bang, again a piston/ring let go on the mag side...

Once opened up, the wash on the piston domes are ideal, but the ring melted to the pistion again with vertival scrapes on 4 sides of the piston..

Now i'm pretty sure this time around it ain't no ''cold seizure''  ...so i'm thinking, should the jetting be modified on the Keihin's just for the ''break in'' period...?

PS I did run 100:1 ratio in the tank on top of injection...

Any help would be appreciated....can't wait to hit the snow for more than 30 minutes...and that goes witouh talking about the $$ invested...

Thanks ..this site is really cool !!

[Interceptor398]

Welcome to the site.  My questions would be is the oil injection set up right and pumping oil? For break in Get a little closer to normal pre mix in the tank for the first take or 2.  Crank seals,  JimVW?

[jimvw57]

I would guess that you have the startings of a melted piston. My first action would be crank seals and a close look at carb boots, fuel pump pulse hose, fuel pump, etc.

If you get an air leak (and it is usually on the mag side)  it will cause a lean fuel condition which makes the sled run great, but too hot for the components and thus melts pistons, cylinders, rings, etc.

another possibility would be if the cylinders were a bit small or the pistons a bit large, once they warm up, could get a bit of interference and give you the marks you are seeing. Once the rings get destroyed, it is hard to tell if the marks are from a melted ring material or cold seizure or what. 

Were you getting smoke out the exhaust from the extra oil? If your oil injection wasn't working, 100:1 isn't much oil for lubrication and cooling.

[gixxer6]

I'd check the fuel system out to make sure its functioning as it should.  Carbs are clean, both fuel pumps working, the pumpers in the carbs working, fuel filters, etc... 

And as the others said, crank seals. 

[Dandb7]

Hey guys,

Thanks for all your help...appreciated...

Here's what's been done to the sled last year before the first meltdown.....Copper and rubber head gaskets replaced oem, crank seals replaced, carbs cleaned, accelarator pump diaphragms checked (no hairline cracks), fuel pumps cleaned (valves and grommets replaced), oil pump and water pump disassembled and cleaned with new o-rings, gas lines, gas filter replaced .........after both breakdowns,  the plugs looked really good (brownish) and so did the wash on the domes.......and yes the extra mix in the tank did make the sled smoke quit a bit but that was ok ...... so where to go from here.....
The melt downs happened both times while running midrange(around 40 mph).......Would going larger on the main jet help just for that powerband and make it richer without affecting too much of the rest of the powerband...? I know the Keihin's are tuff to deal with...but i'd love to keep it stock and ride it that way...

Again thanks so much guys for all your input.....

Regards

[jimvw57]

Just a word of caution, I spent the better part of a year messing with a sled that had 'new seals' put in before I got it. To make a long story short, after months of messing with carbs, coils, CDI, etc, it ended up being a torn brand new seal. seems they didn't lube the crankshaft before they put it back together and on the first startup, it tore the seal.

 thus my nickname and my chant... crank seals crank seals crank seals.....

[Tory944]

  Don't forget to "prime" the oil pump lines... hold pump lever full open on idle to get all the air bubbles out of the lines.  What pistons are you using?  Wiseco pistons need more cylinder wall clearance...  higer sil. content.  They expand more when hot.

[Dandb7]

The pistons are from Bob at Image and the oil lines were primed....

As for the crank seals, i'll make sure that was done right and replace again if necessary......

As anyone ever played with jetting on these Keihin's..?

Thanks guys.

[gixxer6]

Both plugs having good color tells me that it's probably not a lean condition causing the issue.  I'd look closer at the oil injection system rather than the jetting.  Test the oil pump.  I have done this on the bench with an electric drill, it's not real accurate as far as an output test.  But it'll tell you if the darn things working at all.  Was it the same cylinder each failure?  PTO/Mag?  Also check the oil check valves... 

I agree with Tory on the forged pistons needing more clearance.  This should be checked.   

[Dandb7]

It was both times on the MAG side....

Oil pumps will be checked again, so will the oil check valves which luckily i have a spare set...

Will be working on this the next few days and get back to you guys..

Feedback is really helpful...thanks and enjoy the weekend !

[kawhead]

my dealings with kaws over the years has always been a '4 square seizure' is a lean burn.the first year invader airbox was held together with clips, they popped off and the box would seperate, no vac for power jets, a 4 square every time....i think lean in the mid range...

[Tory944]

  I know this doesn't answer you question, but I feel you should be aware of an issue w/those jet ski pistons from Image...   make sure the wrist pin clips DO NOT allow the pin to slide past them when installed.  It seems the clips supplied w/the jet ski pistons were not adequate wire diameter - enough to keep the pin from sliding past.  If in doubt, use some different clips.  Trust me on this one...  it's not a pretty picture when the pin floats past the clip at 8500 rpm.

[Dandb7]

Hey guys,

I need some input on what oil to use (synthetic or mineral) for an engine break-in.....like on a 550 Interceptor...

I get all kinds of opinions on the subject and i really don't know what's best...

Thanks for any advice you can give..

Dan

[gixxer6]

I have always used Klotz fully synthetic, and have never had a problem. 

[kawhead]

i ve used merc premium plus since kaw quit in all my sleds, good stuff