550 Ignition problem?

[Johnny340]

I have a Kawi 550 reed motor which runs absolutely perfect for the first 5 minutes and then it won't rev all the way up as high especially trying to accelerate from low speed. It just vibrates and bogs at a slightly lower RPM. As soon as you stop for a few minutes change nothing, then go out again it's perfect for the next 5 minutes and then the same thing. Changing mixture settings has no effect after 5 minutes either. It's like the spark plugs get too hot or something. I changed plugs and it worked great for up to 15 minutes and then no full rev up...just vibrating bogging at a lower RPM. I think the jetting is good. Why would this problem clear itself after a brief stop? The ignition box it completely dry. Do I need new boots? Here are the BR8ES plugs with about 4 hours on them:

 

[SuperJETT]

The 2 things I'd check are the gas tank check valve and your stator coils' resistance readings.

A quick/dirty test on the check valve is to ride until it craps out, then immediately open the gas cap and see if it has pressure or sucks in. If it sucks in, then the valve isn't letting air in as you use the fuel. You can also just blow into it (hard), it should let air in but not out (until a high pressure relief hits).

On the stator there is a pulser and igniter coil for the ignition. The igniter charges the cdi, the pulser triggers a spark. As they get old, they can fail and start affecting topend first. Heat hurts them as well. I'm sure you can search here or on pwctoday to find the specs. (there is also a charging coil for the battery, it's the 2 green wires)

 

[Johnny340]

I know that the check valve is good. I actually get quite a bit of positive pressure in the tank which hisses out when I take the cap off. Blew the rubber seal off the gas cap once!

I found the specs for the SJ (here) and for a 550SX (on pwctoday). Is the 550 ignition the same as what's in my PJS VHP 7000 Viper? How could I tell?

Here are the resistance specs for a 550SX stator if anyone else is searching here for them:

Exciter Coil Red (or purple) & Black 112-168 ohms +/- 20%

Pulser Coil Red (or purple) & Gray (or green) 14.4-21.6 ohmsPulser +/-20%

Charge coil - Green (or lt brn) ----- Green (or lt brn) - 3ohms +/- 20%

Green (or lt brn)-----Black - 1.5ohms +/- 20%

Here are a few pictures to help identify what I'm dealing with:
The electrical box with cover off: (Never mind the 'Captain Crunch' cereal box gasket.)

Is this the Igniter (exciter) coil?

The CDI?:

The wires from the Stator. (purple and green for pulser Coil? I get 16.2 ohms.)

Thanks a lot for your help here.

 

[ger87410]

My 550 doesn't have a check valve. I've not found a need for 1...

 

[Johnny340]

OK, ignore my ignorance in my previous post.
I have figured out that everything is on the stator and I get:
136.6 ohms for the Exciter coil
16.2 ohms for the Pulser coil
2.9 ohms for the Charge coil
If the stator is like the 550 one then I am within spec here.

So why would it be only running right during the first five minutes or when I put new plugs in? Could any of these coils be bad only when hot? I was thinking of replacing my spark plug boots or is that stupid? I assume BR8ES plugs at .7-.8mm is the way to go. yes?

 

[ger87410]

Test the stator with it cold.

Put the stator in boiling water for 5 minutes and then run the test again.

Compare the 2 readings.

Heat can do STRANGE stuff.

 

[Johnny340]

I never thought of that way to heat it up.
I heading out today and I'll see if these new plugs last longer now that I put on new boots. The ends of the old leads were hardened and had a few wire strands broken. If this makes no difference then I'll get out the pasta pot...
Thanks.

 

[Johnny340]

With new boots and plugs everything seems to be running fine. I had it out for a couple hours and the problem never occurred. The water was really rough though and the pump and engine were constantly being offloaded so the true test will be in calm water during this coming week of camping.

 

[cosander]

I once had a 550 with a loose stator that would shift the timing from advanced (ran good) to retarded (ran retarded).

 

[Johnny340]

I thought it was good but it still craps out after 10 minutes. I change the plugs and it runs perfect for another 10-15 minutes. Now I think it's just the cooling time that actually makes the difference, not necessarily the new plugs. When it runs worse (when too hot?) it runs good in all ranges except wide open. It's almost like the rev limiter is cutting it out too early when it gets too hot. Is that possible?

Thanks for any opinions. I'll check the stator mounting bolts next.

 

[Johnny340]

Stator is tight.

What about disconnecting the Rev limiter to trouble shoot? Is the rev limiter wire the Grey wire (between the purple and green wires) in the second picture?

 

[Johnny340]

The rev limiter is the green wire. More importantly, someone noticed that the green and purple wires were reversed as seen in the first pic. It even had a heat shrink over the connection with PJS labeled on it but you could still disconnect the wires with the heat shrink in tact. Wires switched, problem solved! 'Keep it Simple Stupid' comes to mind. Can't believe I didn't question that setup before....