KawasakiTrax Community
General Category => The Interceptor Gang => Topic started by: gixxer6 on December 12, 2012, 07:35:05 PM
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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?
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No one has jetting specs for Mikuni's on an Interceptor???
Currently it has:
6DH2 Needle
Q2 166 Needle Jet
35 Pilot
350 Main
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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
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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.
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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...
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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!
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Did you do a leak down test?
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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.
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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......
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After fighting with my Intruder I sheepishly suggest checking to make sure that the primer is not leaking.
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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. 8)
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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?
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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.
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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?
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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.
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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?
I built the primary clutch for this sled. It is all stock with all new bushings. I did take it apart to double check everything was still in place.
I don't recall what all was done with the secondary. It's been awhile since I have messed with this sled. I will take a closer look at it.
Thanks for your input.
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if you see an improvment with smaller jets/cooler temps it leads me to think leaner will help....sounds like you are getting extra fuel somewhere....
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Update:
I dropped another 20 points off the mains. It isn't perfect, but it's ALOT better. It'll pull almost full RPM. It'll bog off the line, then pull the skis, up til about 7,800 RPM, then it'll slowly gain RPM up to around 8100. Which is still a little low, but at least I know I'm on the right track. I'm going to drop the needle one clip, and maybe the main another 10 points. I'm a little confused why others are running 350 mains, and I'm all the way down to 310's???
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You are running with and airbox right? I had 340's with velocity stacks and its was a bit rich. with and airbox i ran as low as 270's
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You are running with and airbox right? I had 340's with velocity stacks and its was a bit rich. with and airbox i ran as low as 270's
Ahhh... That explains it. Thank you.
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Trucker, Do you remember what pilot, needle, and needle jet you ran when you had the airbox on? Thanks.
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Same and only once because it ran crappy with it.
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Ran crappy with it? The airbox???
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yes it ran crappy with the airbox so i just used the velocity stacks
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Trucker, were you running 38's or 39.5's?
I switched my airbox for velocity stacks and installed 350 mains. It is WAY better. Thanks again for the info. Here is where I am at:
350 main
2.5 slide
6DH2 middle clip
Q-0 needle jet
40 pilot
It runs fairly good, but isn't quite right yet. I'm going to try a fresh set of plugs, the current plugs have been through the ringer while jetting it. They've been fuel soaked countless times.
I don't like the extra noise with the velocity stacks. Anyone every try running a gutted airbox???
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I had 39.5's and yes the extra noise is annoying. go bax to using your airbox but make sure its cleaned out good inside and try smaller jets until its right.
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New plugs installed. Its sluggish off the line, but after the first 10 feet it pulls hard and runs a good 8,300 rpm. The plugs look light brown, but it was REALLY cold when I ran it. The 350 mains should produce a nice chocolate brown in warmer temps.
Any ideas why it'd be sluggish out of the hole? Maybe they're all a little sluggish???
I am toying with the idea of rebuilding the stock Keihins, just to get a baseline of what stock performance is.
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Air screw and pilot jet affect off idle performance. My 550 cats had the same carbs with #35 pilots and about 1/2 turn out on the air screw. Might be worth a try? The air screw is very sensitive to small adjustments but really cleans up the bottom end.
Good Luck ;)
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Air screw and pilot jet affect off idle performance. My 550 cats had the same carbs with #35 pilots and about 1/2 turn out on the air screw. Might be worth a try? The air screw is very sensitive to small adjustments but really cleans up the bottom end.
Good Luck ;)
Me again, screwing in the air screw makes it richer-out leaner(more air) you have 3 turns of adjustment. The ideal setting is about 1 - 1 1/2 turns out putting you in the middle of the adjustment for that circuit. Just keep changing the pilot jet until you get to that.
Kevin
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Just as a baseline, I cleaned the stock carbs on mine last night. I then took it out and put a few miles on it as I am heading to a vintage ride with it today. It runs very strong pretty much right off the line. It will spin the track off idle. The problem I'm having and maybe it's just old technology but off the line she pulls hard and rocks out nicely. After I get to a nice cruising speed of about 30 or so then punch it, it's a little boggy until the motor ramps up again. I believe mine is a clutching issue with a sluggish backshift. I've never had my secondary apart so I don't know if I would benefit from a clean up or if this is what to expect out of old technology.
As a side note, I have talked to many who say that they could get their 550 running good with the Mikuni's but never quite as good with the stock butterflies. That's why I have stuck with the stockers even though they are a pain to take apart and clean and are harder to find parts for.
Robb
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I know this thread is old but I am intrigued by this. Doesn't the stock Interceptor carb have an accelerator pump on it? If so then this is probably the reason the stock carbs work better. The pump gives it the extra shot of fuel it needs to make a smooth transition from idle to mid range. I think that while the pilot jet and idle mixture are fine for idling on the 38mm carbs they are too lean to make a smooth transition to higher rpms. I think that experimenting with different jet needle tapers and/or a bigger pilot jet might solve the problem.
I'll probably find out if I acquire a wreaked Interceptor next month. Hopefully.