#553

[gixxer6]

After a complete engine rebuild on my daily driver (99 MXZ670HO), I'm finally getting back to #553.  I resealed the heat exchanger that sprung a leak over the summer.  I "restored" it last season, but never got it running quite right.  It seems to run and idle ok, but its hard to start when warm, and doesn't make good power.  I thought maybe the timing was off, but I checked it, and its right on.  Iirc, the carbs are 38mm Mikunis bored to 39.5's.  The engine is stock, with stock pipes, and an airbox installed.  I don't remember what jets I have in it.  Anyone have jetting specs for this setup? 

[gixxer6]

No one has jetting specs for Mikuni's on an Interceptor??? 

Currently it has: 

6DH2 Needle
Q2 166 Needle Jet
35 Pilot
350 Main

[Kawasaki Powered]

Here's what I have saved for jetting the 38's

Main Jet 350 to 370
2.0 slides, but 2.5's work too
40 pilots
Q-O's with 6DH7's in the middle clip

Robb

[gixxer6]

Here's what I have saved for jetting the 38's

Main Jet 350 to 370
2.0 slides, but 2.5's work too
40 pilots
Q-O's with 6DH7's in the middle clip

Robb

Thanks Robb.  I'll start there.  I think I have all of these parts, other than the 2.0 slide. 

[gixxer6]

How much difference is there between Q-0's and Q-2's?  I'm running:

350 mains
35 pilots
2.5 slides
Q-2's
6DH2's in the middle clip

And it runs absolutely terrible.  I can hardly get it to rev over 7,000 rpm.  And it refuses to make power. 

I've got Q-0's on order, but I think I may have another problem...

[gixxer6]

I changed my jetting to: 

6DH7 Needle, middle clip
Q0 Needle Jet
2.5 slide
40 Pilot
350 Main

It still runs terrible.  I am running out of patients quickly, thoughts of parting the sled out are crossing my mind.  I rebuilt the entire sled from the ground up over a year ago, and I have been trying every since to get it running right.  The NOS odometer reads 32 miles, all of which were painful. 

It will start and idle good.  When I hit the gas, after a sluggish hole shot, it pulls strong (lifting the skis) until it hits 7,500ish rpm, then it will bog and lose rpm.  It doesn't appear to be affected by the amount of throttle input.  The longer I hold the throttle, the more rpm it looses.  Plugs are a grayish brown color and are typically wet when checked.  It doesn't seem to smoke excessively, so I assume the oil injection is working properly. 

A little history on the sled:  rebuilt crank from Crankshaft Services, new crank seals, all new gaskets, stock bores, stock porting, uncut head, stock pipe, 39.5mm Miks, Invader airbox, stock rebuilt clutches, timing has been set per the manual, new high flow single mikuni fuel pump, carbs are not setup for a primer, new belt, all new fuel lines and filter, running Klotz oil. 

What I have tried/checked:  Swapped the pipes, CDI box, and coils.  Cleaned the airbox, checked the pipes for mouse nests, verified the oil injection was set correctly, several sets of new BR9ES plugs, I have only roughly synced the carbs, verified the carbs were opening all the way.  Fresh premium fuel (same fuel that runs great in my other sleds), there is no fuel in the pulse line, and probably more that I am forgetting... 

Anyone have any ideas???  I have built MANY snowmobiles (a few Invaders), motorcycle's, but this is my first Interceptor.  I am a technician trained in troubleshooting, but this thing has me STUMPED! 

[Interceptor398]

Did you do a leak down test?

[gixxer6]

Did you do a leak down test?

I did not.  It is a freshly sealed motor, so I assume it would pass.  But I am running out of things to try, so I will consider trying this. 

[kawhead]

if it idles good the seals should be ok.....after all thats been tried,[same stuff i'd do]i'd drop 20 points off the main jets to see if it improves......

[mswyka]

After fighting with my Intruder I sheepishly suggest checking to make sure that the primer is not leaking.

[gixxer6]

After fighting with my Intruder I sheepishly suggest checking to make sure that the primer is not leaking.

While normally I hesitate to say ANYTHING with 100% certainty, I am absolutely certain that the primer is not leaking.  This Interceptor doesn't have a primer, or the nipples on the carbs to hook one up.   

[gixxer6]

if it idles good the seals should be ok.....after all thats been tried,[same stuff i'd do]i'd drop 20 points off the main jets to see if it improves......

I agree, I have expereinced bad crank seals and a leaky base gasket, and this case does not show any of the symptoms. 

I took your advice, I picked up and installed 330 mains tonight (down from 350's).  It will now run a fairly consistent 7,000 max rpm.  However I'm not sure that the jets had anything to do with it.  It is about 25 degrees cooler than the last time I ran it. 

What should I do next?  Try 310's? 

[The Great Jashu]

I dont have an Interceptor, and I dont know as much as you regarding any motor. But reading through what you have done I was intrigued by the "timing set per the manual" quote. Does this need to advance as RPMs come up? Could it be something with that?
Just my humble thoughts.

[Invader440]

It will now run a fairly consistent 7,000 max rpm.

Doesn't sound right.  Looked in the service manual and it should be running around 8200-8300 max rpm.  Have you checked your clutches or checked to make sure the slides are opening all the way?

[gixxer6]

I dont have an Interceptor, and I dont know as much as you regarding any motor. But reading through what you have done I was intrigued by the "timing set per the manual" quote. Does this need to advance as RPMs come up? Could it be something with that?
Just my humble thoughts.

The timing is set by making a mark on the clutch at a specific distance BTDC of the PTO piston.  Then running the motor with a timing light to 6,500 RPM and verifying that the mark is aligned.  If it is not, the stator plate must be turned to adjust.  Once set at the specific RPM, the CDI advances and retards ignition as needed.  My initial thought was the CDI was not doing its job, so I swapped it with another CDI and nothing changed.