f7 cylinder

[garyl62]

A buddy of mine is replacing the cylinder on his 05 f7. I don't have many details but he asked me to post a couple photos to see if I could get some info to help him out. I think he only has one new one now and when he pulled the old one it has a hole that has been machined into the side. His replacement doesn't have the same hole.

Can anyone tell me what that is for, how it may have been done, and if he can just replace it with the one without the hole? He doesn't know if the other one has the same hole or not, but would guess it does. What happens if he put this one in and they aren't the same?

 

[ezra]

got some in side shots ? that is a odd hole . obviously some one was tinkering with it big time. that is why I want to see both jugs cuz if that was done I would bet they are ported and u cant mix and match ported and un ported jugs.

 

[garyl62]

I'll see what I can get. Obviously this one is out and I'll get more shots, but I don't they've pulled the second one out.

 

[ezra]

should be able to get a good look with piston on bottom of jug on rotation to compare ports or just compare the one that is out to the new one should be pretty clear if the old one had work done . we are assuming he got this thing 2nd hand

 

[garyl62]

After looking at them some more, I think someone did some home brew work. Not sure why, the piston never goes below the hole so it’s not like it adds any to the intake, not sure if the guy thought it would add some lubricant to things. I'll post the photos, but it seems like when I post photos now I never know what order they will actually show up in, so I'll describe them in the order I think they will be, but you should be able to figure it out.





Looking down the jug without the piston. You can see the hole lining up with the intake.

Looking down again, this time on the bench. You can see a little more of the cylinder.

Piston at bottom of stroke. Doesn’t even get to the hole.

Piston at bottom of stroke, from the outside.

Here are both jugs together. The holes aren’t even the same shape. My buddy is thinking he may just drill out the new one in a shape similar. I told him just buy another one that is stock and be done with it.


Any thoughts?






- - - Updated - - -

OK, I can't even edit that post, but the pics came out in the order I expected, except the first one I described is actually the last one. The rest are in the order I said.

 

[garyl62]

Any other ideas or thoughts?

 

[G]

The extra holes are on the exhaust side. The only thing I can think of is the guy was trying to cool the exhaust side of the piston with a little fuel at low stroke. This in theory would allow slightly leaner jetting for more snap. It might work for an on throttle - off throttle type of riding but full WOT for any distance would probably still burn it down. AC made some motors with hotspots in the ignition curve that could burn a sled down also. My ZR 900's have a narrow lean spot in the midrange that they basically never figured out. They tried about 47 jet needles and never did get it right. They never got it right later on with the EFI 900's either. That is why you have to be so careful when you pipe or otherwise modify them. Your holes don't look like they have much to do with intake porting. I have never seen anything like that before. I really have no idea but for my money they are for cooling the exhaust side of the piston with raw cool fuel. Wait a minute. Maybe they were trying to heat and expand the cool fuel circulating through the transfer ports with the hot side of the piston at low stroke. This might expand the volume of the fuel mixture giving it a greater power stroke. I really don't know. Just guessing.

 

[mjkaliszak]

After looking at them some more, I think someone did some home brew work. Not sure why, the piston never goes below the hole so it’s not like it adds any to the intake, not sure if the guy thought it would add some lubricant to things. I'll post the photos, but it seems like when I post photos now I never know what order they will actually show up in, so I'll describe them in the order I think they will be, but you should be able to figure it out.





Looking down the jug without the piston. You can see the hole lining up with the intake.

Looking down again, this time on the bench. You can see a little more of the cylinder.

Piston at bottom of stroke. Doesn’t even get to the hole.

Piston at bottom of stroke, from the outside.

Here are both jugs together. The holes aren’t even the same shape. My buddy is thinking he may just drill out the new one in a shape similar. I told him just buy another one that is stock and be done with it.


Any thoughts?






- - - Updated - - -

OK, I can't even edit that post, but the pics came out in the order I expected, except the first one I described is actually the last one. The rest are in the order I said.

That hole is a butcher job ( JIMO ).... you need both cylinders the same, when it comes to porting, the only reason for radical porting is some clutching set-up that I can't imagine... I will take a guess that they were trying to get more lube around the skirt. I may be wrong but I thought that 5th porting is something different. I also thought that it is/was best to have cold fuel squirting into a hot chamber, hot /warm fuel will alter the volume that is occupied with air, oil, gas....
I wouldn't put those in 1 of my builds, maybe see if you can get some reconditioned Stockers....or NEW better yet. Never built a grenade !

 

[ezra]

any idea who was 1st owner?

 

[G]

It is a butcher job. But if it isn't porting to improve or alter fuel flow I don't know that it matters if it isn't pretty. This is really interesting though. I hope somebody can find out the why.

 

[Wong]

The cylinder with the hole is from an EFI motor and the one without the hole is from a carb model. The hole is a compression release port. Don't mix and match if you want a long running reliable motor.

 

[raceinsnow]

When you put the cylinder in the case the hole lines up with the intake port to let the fuel air charge into the crankcase. This is not a compression release port.

 

[G]

My ZR 900 has compression release port. It is a little tiny hole 3/4 of the way up the cylinder wall. Like about a 1/8 inch drilled hole. I believe it vents into the variable exhaust manifold. What you have on that F7 is not a compression release port. Also I thought all the F7s were EFI's. No carbs on any of them.