Did you install the resistor? SLP instructions say to install the egt resistor above 5000' with the pipe, head & intake.
Significant loss of RPM after adding head to SLP single pipe.
- Thread starter Ken Climb
- Start date
Any fix for this?
Is this a 2016 RMK?
I just noticed your post and I am sure I can help.
I will assume it is a 2016 RMK.
Naturally when you increase compression rpm will drop a little but not what you are seeing.
1 – When you add the SLP head it adds more power. It always will need a little more clutch weight to compensate for the additional power. If you don’t add the weight the engine becomes “unloaded” then combustion goes cold and rpm will drop substantially, just as you experienced. More weight will load the engine more, combustion temperature comes up and makes power and rpm.
The most common and best clutch setup for 6000-8000 feet is the blue/pink spring with 68 gram MTX weights with 3 gram in the tip and 1 gram on the inner hole with the stock secondary spring and helix. The black/purple at that altitude would have unloaded the engine more.
If you are getting rpm but not up to 8300-8400 then add 1 more gram to the inner hole.
Also the Polaris weights will tend to be a little more revy than the MTX so they will not load as well even if both run the same peak rpm.
2 – The 6000 ft head is designed for 6000 ft and higher on 91 octane fuel. If you go lower altitude it will require more octane or if you are 6000 ft and higher with less than 91 than rpm will drop. This is caused by the engine sensing detonation and retarding the timing. Getting good fuel can be a crap shoot as it is so if you have any question about fuel quality add some of the Lucas octane booster.
3 – Sleds like cars and about everything else are not all created equal or at least exactly equal. Some engines may be slightly richer than others and may run fine with one setup and not another. This is common when the TPS is not correctly adjusted as well. One test to do is to remove the exhaust probe resistor and see if rpm changes.
There are other variables as well like exhaust valve function, weak ignition not being able to support the higher compression and so on. One this to be sure of is if you have installed an “advance key” on it be sure to remove it.
Let me know if this does not help you fix it.
I will assume it is a 2016 RMK.
Naturally when you increase compression rpm will drop a little but not what you are seeing.
1 – When you add the SLP head it adds more power. It always will need a little more clutch weight to compensate for the additional power. If you don’t add the weight the engine becomes “unloaded” then combustion goes cold and rpm will drop substantially, just as you experienced. More weight will load the engine more, combustion temperature comes up and makes power and rpm.
The most common and best clutch setup for 6000-8000 feet is the blue/pink spring with 68 gram MTX weights with 3 gram in the tip and 1 gram on the inner hole with the stock secondary spring and helix. The black/purple at that altitude would have unloaded the engine more.
If you are getting rpm but not up to 8300-8400 then add 1 more gram to the inner hole.
Also the Polaris weights will tend to be a little more revy than the MTX so they will not load as well even if both run the same peak rpm.
2 – The 6000 ft head is designed for 6000 ft and higher on 91 octane fuel. If you go lower altitude it will require more octane or if you are 6000 ft and higher with less than 91 than rpm will drop. This is caused by the engine sensing detonation and retarding the timing. Getting good fuel can be a crap shoot as it is so if you have any question about fuel quality add some of the Lucas octane booster.
3 – Sleds like cars and about everything else are not all created equal or at least exactly equal. Some engines may be slightly richer than others and may run fine with one setup and not another. This is common when the TPS is not correctly adjusted as well. One test to do is to remove the exhaust probe resistor and see if rpm changes.
There are other variables as well like exhaust valve function, weak ignition not being able to support the higher compression and so on. One this to be sure of is if you have installed an “advance key” on it be sure to remove it.
Let me know if this does not help you fix it.
Last edited:
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