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The bike is not running right and feels very low on power already. I think I found out why the 220 was running badly. The entire engine was sent to FRP and everything was perfect when I got it back. It started to run bad by the 2nd hour. Figured I needed to mess with the jetting. I did a compression test and only got 90 psi after 4 hours of ride time. How could this have happened so quickly? I followed the instructions given for the break in. I was running 32:1 but found out at 3 hours I should’ve been running 52:1. I ran out of fuel twice when the engine was fully warmed up. One of the times was actually because I forgot to turn the gas on. The other was simply because the petcock needed to be switched to reserve. Thanks

Hey so I think I found out why the 220 was running badly. The entire engine was sent to FRP and everything was perfect when I got it back. It started to run bad by the 2nd hour. Figured I needed to mess with the jetting. I did a compression test and only got 90 psi after 4 hours of ride time. How could this have happened so quickly? I followed the instructions given for the break in. I was running 32:1 but found out at 3 hours I should’ve been running 52:1. I ran out of fuel twice when the engine was fully warmed up. One of the times was actually because I forgot to turn the gas on. The other was simply because the petcock needed to be switched to reserve. Thanks

Only a guess but when it was assembled did you put plenty of oil in the crankcase, you may have run it dry and damaged the crankcase seals

Either an air leak, you ran it way too lean (which running it out of gas does but shouldn't have been enough to hurt it, or you sucked some dirt in. BTW, did you check the ring gap? Did Fredette say he did that? Also, why should you have been running 52:1 mix? That is not a common mix ratio for the KDX.

SS109 wrote: ↑01:10 am Jul 09 2022 Either an air leak, you ran it way too lean (which running it out of gas does but shouldn't have been enough to hurt it, or you sucked some dirt in. BTW, did you check the ring gap? Did Fredette say he did that? Also, why should you have been running 52:1 mix? That is not a common mix ratio for the KDX.

I took apart the air box completely and reassembled before putting the engine into the bike. I never asked Jeff if he did the ring gap or not because I assume he did everything correctly. He recommended 52:1 when it comes to using the golden Spectro oil.

kdxdazz wrote: ↑11:36 pm Jul 08 2022 Only a guess but when it was assembled did you put plenty of oil in the crankcase, you may have run it dry and damaged the crankcase seals

FRP assembled the engine so I wouldn’t know but I’m sure it was done right.

Before you pull it apart I would do a leak down test to see if there’s an issue you can pinpoint.

^^^^ Agreed, get a leak down test done.

What is your technique on measuring the compression?

Can you please post a picture of the end of the spark plug?

Thank you.

I held the throttle wide open and kicked till the psi reached its peak at 90psi

Was that a fresh plug?

Did you measure the compression when you first assembled the engine? This needs to be done first to establish a base line for later tests.

Also, where is the Schrader valve on your compression tester, at the gauge or in the spark plug adaptor at the end of the hose? If its at the gauge, you're not getting a true reading since the hose volume is added to the combustion chamber volume, which lowers the overall max reading. You need to have the Schrader valve in the spark plug adaptor to get a true reading.

Do a Google search on "The Truth about Compression Testing" for more info on this subject.

pumpguy wrote: ↑04:11 pm Jul 10 2022 Did you measure the compression when you first assembled the engine? This needs to be done first to establish a base line for later tests.

Also, where is the Schrader valve on your compression tester, at the gauge or in the spark plug adaptor at the end of the hose? If its at the gauge, you're not getting a true reading since the hose volume is added to the combustion chamber volume, which lowers the overall max reading. You need to have the Schrader valve in the spark plug adaptor to get a true reading.

Do a Google search on "The Truth about Compression Testing" for more info on this subject.

I didn’t check as it was assembled professionally by FRP. The Schrader valve is in the actual gauge that goes on the end off the hose. Will it really effect it that much? I would hope to have a reading of 140-150psi and not sure if that would effect the numbers that much. Thanks

Go to the parts store and rent one, I bought one from harbor freight with just gauge had schrader valve and was only getting 90psi, so I rented one and got 144psi, I returned the harbor freight one and ordered a better branded one on Amazon and got 145psi

DonnyV wrote: ↑10:55 pm Jul 10 2022 Go to the parts store and rent one, I bought one from harbor freight with just gauge had schrader valve and was only getting 90psi, so I rented one and got 144psi, I returned the harbor freight one and ordered a better branded one on Amazon and got 145psi

I just ordered a motion pro compression tester. Always had good experiences with motion pro so I’m sure it won’t lie. The one I used was a 20 dollar Amazon gauge. I’ll report back on what reading I get. The bike runs like crap right now so I’m actually hoping it still reads low. I thought prior to the 90 psi reading that maybe it could be jetting but seems like it’s running way more off then jetting would be able to cure. Thanks

Crazy question, but would it not be pretty easy to kick over at 90 psi? Did the "difficulty to kick it" change from then to now?

KDXGarage wrote: ↑07:12 am Jul 12 2022 Crazy question, but would it not be pretty easy to kick over at 90 psi? Did the "difficulty to kick it" change from then to now?

I actually didn’t notice it getting any easier. But I can push it down with my hand with a much shorter kick starter than stock. Took it for another ride yesterday and obviously still doesn’t feel so smooth. Also its not putting down the power I would expect. In 4th gear for example I can barely lift the front end let alone 5th - 6th. I hear a lot of people say with the FRP engine build that they find themselves being able to ride a gear higher. I have lost that feeling which I initially seemed to feel. Especially going up a hill in tight trails that I should be able to go up in second but instead I am in 1st. Thanks

Stop riding it until you figure out what's going on. You could possibly be creating even more damage to the engine.

What are those sparkly shiny aluminum specks on your plug?

Molly's 70 wrote: ↑03:41 pm Jul 12 2022 What are those sparkly shiny aluminum specks on your plug?

I think they are from sitting open in the garage for a few days. I swapped the plug at one point so it was just lying around for a bit.