High compression
Seasoned HDF Member
Joined: Mar 2010
Posts: 20,851
Likes: 7,391
From: Poolville
Timing tables look good.
The thing I don't understand is why you went with the 26 cams they are more for stock motors. The 37 I feel would have been more appropriate. The 54 is a little much for your compression. That cam likes 10.2-10.4 compression not only that you never mentioned what was done to the heads and what head gasket you're using. It's hard to make suggestions without all the motor build info and how you like to ride.
As Max said though, if you like it and it fits your style of riding there is no need to change. Sea Foam is your friend.
The thing I don't understand is why you went with the 26 cams they are more for stock motors. The 37 I feel would have been more appropriate. The 54 is a little much for your compression. That cam likes 10.2-10.4 compression not only that you never mentioned what was done to the heads and what head gasket you're using. It's hard to make suggestions without all the motor build info and how you like to ride.
As Max said though, if you like it and it fits your style of riding there is no need to change. Sea Foam is your friend.
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Road Captain
Joined: Aug 2018
Posts: 583
Likes: 91
From: Stockholm
Heads are just milled about 0.2 mm and are around 50 cc.
MLS 0.040”
Deck heights 0.005 and 0.002 below.
Piston dome 1.2
Static compression 1:9.6
Yep, heard good about 37. You think the piston to valve clearance will be ok with that cam?
MLS 0.040”
Deck heights 0.005 and 0.002 below.
Piston dome 1.2
Static compression 1:9.6
Yep, heard good about 37. You think the piston to valve clearance will be ok with that cam?
Last edited by OakMountainRider; Dec 9, 2024 at 06:46 PM.
Seasoned HDF Member
Joined: Mar 2010
Posts: 20,851
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From: Poolville
It should be fine. It's designed as a bolt in cam for a stock motor. I would talk to the person who installed your pistons.
Hold it, your heads were milled, and the combustion chambers are 50 cc.. And what is piston dome 1.2??
If I'm reading this correctly you compression is a lot higher than you think..
Hold it, your heads were milled, and the combustion chambers are 50 cc.. And what is piston dome 1.2??
If I'm reading this correctly you compression is a lot higher than you think..
Last edited by 98hotrodfatboy; Dec 9, 2024 at 08:18 PM.
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Road Captain
Joined: Aug 2018
Posts: 583
Likes: 91
From: Stockholm
It should be fine. It's designed as a bolt in cam for a stock motor. I would talk to the person who installed your pistons.
Hold it, your heads were milled, and the combustion chambers are 50 cc.. And what is piston dome 1.2??
If I'm reading this correctly you compression is a lot higher than you think..
Hold it, your heads were milled, and the combustion chambers are 50 cc.. And what is piston dome 1.2??
If I'm reading this correctly you compression is a lot higher than you think..
I have grinded the chambers to accommodate them to the difference in deck height. Average CC is 50.1.
The milling, done by a machine shop, (who also drilled for the compression releases), was done before I grinded the chambers to average 50.1 CC and it should be only 0.2 mm. This would be 0.008”. But should not effect the compression as I adjusted that through the chambers.
The cylinders were bored by another small machine shop, (founded 1958 by the guy´s grandfather). I installed everything myself.
Link to the piston at JE: https://www.jepistons.com/product/je...-bore-right-4/ As the site says it is a 1:9.5 piston.
Here is the piston package, it says 1.2:
Last edited by OakMountainRider; Dec 10, 2024 at 06:11 AM.
Seasoned HDF Member
Joined: Mar 2010
Posts: 20,851
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From: Poolville
With everything you say you have in the motor w/50 cc heads your comp would be 14.8:1.. To get to 9.6:1 you would have to have 85 cc combustion chambers, and you should have no issues with the 37 cams. Forget the 54 because your early heads with stock springs will not accept cams with a lift above .520"
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Road Captain
Joined: Aug 2018
Posts: 583
Likes: 91
From: Stockholm
With everything you say you have in the motor w/50 cc heads your comp would be 14.8:1.. To get to 9.6:1 you would have to have 85 cc combustion chambers, and you should have no issues with the 37 cams. Forget the 54 because your early heads with stock springs will not accept cams with a lift above .520"
Front is 84.8 and rear is 85.2 CC. Deck height front is 0.005 and deck height rear is 0.002.
I am sorry for creating this confusion. I must have had a "momentary laps of reason", as Pink Floyd would have put it.
Road Master
Joined: May 2018
Posts: 772
Likes: 177
From: Bay Area
Thanks Max, it is always great to get opinions, experiences and knowledge through this forum.
I have actually scratched my head more than twice wondering why my Cold Cranking Compression is so high. I even sent my manometer to be checked, as I thought it showed too much. It did, but not that much.
Been thinking of Andrews 37, or even 54, to bring the compression down, but have not decided yet. Maybe I just seafoam it this spring.
Anyway, bike runs fine and does not ping anymore, in as the ECM does not count any knocks - this after I Autotuned it several times and pulled timing 18 % from the tune (received from Dynojet when I changed to Andrews 26). Especially it stopped pinging after I removed the DK Custom torque plates in my baffles, which made it ping as soon as I twisted the throttle.
(When I say pinging I refer to knockcounts seen on the Power Vision. I have not heard any sound as my hearing is not so good.)
I have actually scratched my head more than twice wondering why my Cold Cranking Compression is so high. I even sent my manometer to be checked, as I thought it showed too much. It did, but not that much.
Been thinking of Andrews 37, or even 54, to bring the compression down, but have not decided yet. Maybe I just seafoam it this spring.
Anyway, bike runs fine and does not ping anymore, in as the ECM does not count any knocks - this after I Autotuned it several times and pulled timing 18 % from the tune (received from Dynojet when I changed to Andrews 26). Especially it stopped pinging after I removed the DK Custom torque plates in my baffles, which made it ping as soon as I twisted the throttle.
(When I say pinging I refer to knockcounts seen on the Power Vision. I have not heard any sound as my hearing is not so good.)
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Road Captain
Joined: Aug 2018
Posts: 583
Likes: 91
From: Stockholm
With everything you say you have in the motor w/50 cc heads your comp would be 14.8:1.. To get to 9.6:1 you would have to have 85 cc combustion chambers, and you should have no issues with the 37 cams. Forget the 54 because your early heads with stock springs will not accept cams with a lift above .520"
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