cutting on my engine- did I go too far? (pics)

[Fletch]

the transition(the edge)between the crome and aluminum needs to be hit wth a cratex wheel and smoothed over Champer so the chrome dont peel the ball hone is for the final procedure it puts crosshex's in the bore so that the rings seat well The bore measures 1.851+ or minus .0005.its all about clearance and friction. good luck

Ken,

Do you use the cratex wheel by going through the ports from the outside, or do you use it directly on the inside of the cylinder?

Then you use the 2" ball hone? What grit?

Is this process correct then?

1) remove flash casting with dremmel

2) use cratex wheel to even out surface

3) use ball hone

 

[ken murphy]

cylinder prep

Ken,

Do you use the cratex wheel by going through the ports from the outside, or do you use it directly on the inside of the cylinder?

Then you use the 2" ball hone? What grit?

Is this process correct then?

1) remove flash casting with dremmel

2) use cratex wheel to even out surface

3) use ball hone

Yes you got it!Becareful as not to score the bore,I wasn't aware there were diferant grits on the hone,I was just happy to get a 2" hone.
Remember your not taking any stock just putting tiny grooves so to rings will seat better,and yes again on the approach from the inside it's the only way to get to the edge.
It's not the flash your remove'n,Its the ecess chrome.
1 more thing on those shift kits,to me it's 1 more thing to go wrong or work on.I already have to many its a chore keep'n 5or6 of em ready to roll.

Happy trails

 

[Deleted member 12676]

porting intelligently

If you want to know how to port for correct timing depending on the powerband you want then click on the link below. I am opposed to the willy-nilly method of porting that is thrown around on this forum. There is a science to porting correctly and it includes the port width as well as when the port begins to open. Without knowing what you are doing you are more likely to end up with a dog of an engine.

Porting tips: http://www.dragonfly75.com/motorbike/

 

[Fletch]

Thanks Jaguar... I'll check it out. The engine was running well with my random porting until I messed with the transfer ports on the inside of the cylinder. I got rid of the little lip on them and now I bog down. I'm replacing the cylinder. I was going to use the piston I cut the skirt on to clear the intake at TDC, and leave the ports alone?

 

[Deleted member 12676]

It comes ported pretty good for low rpm power. If you want it a little peppier then do this :
raise the exhaust 1mm
raise the transfers .5mm
lower the intake 1mm (or cut the piston intake skirt) and widen it by 2mm on each side.
More important than those changes is shaving down the cylinder head for more compression. Take .5 to 1mm off. There was a .5mm lip on mine that I got off easily enough using sandpaper and thick glass (as a very flat base to place the sandpaper on). Then the metal surface was much larger and going was very slow and I gave up except for making a thin copper gasket for it to replace the stock one.

 

[Fletch]

Hey guys,

I installed a new block with no port mods, but I used the piston that has the cut skirt (clears intake all the way at TDC), and I didn't use a base gasket or head gasket. I didn't intentionally shave down the head, but I did take a bit off by sanding it smooth. I also sanded the block where they join, and I'm using an expansion chamber exhaust. I haven't been riding these bikes long, and I started out using the CNS carbs so I don't have a real good feel of what a stock engine/carb performs like, but I've noticed a couple things....

First... The engine idle speeds up as I roll down hill with the clutch disengaged. My logic was that the clutch wasn't fully disengaging and this was causing the increased idle. So I messed around with the clutch going back and forth with the acorn nut and I just can't get it set to where it both, engages and starts well, and cruises downhill without increased idling. The increase in idle is minor, but I have never noticed it on my 2 builds before this. Now I am wondering if the clutch isn't the reason but maybe it has something to do with the timing, or the expansion chamber keeping more fuel in the cylinder longer or something? I also noticed that after I slow down from high speed... the idle remains higher and then slowly drops down to baseline again. Maybe it's not the idle I am noticing, but the engine still turning and burning up fuel? I have no idea.

Even with no base gasket or head gasket, and having sanded the head/block... the longer than normal NGK spark plug is not hitting the piston.

My questions are:

1) the idling increase?
2) What do you guess I did to my timing/engine?
3) Is it detrimental? (Ie. should I replace the piston with a non-skirted one? or make any other changes? Will it shorten the life of the motor?)
4) What do you do when you are hauling *** downhill with the clutch disengaged and you get to the bottom of the hill where you want to give it gas again? When I engage the clutch going that fast it seems really hard on the engine and actually slows it down I think.

Thanks!

 

[Deleted member 12676]

Lowering the cylinder makes better port timing for low rev power. If the bottom of the intake port is lowered more than 1.5mm from stock then that makes it hard to start and robs low end power. The base gasket is maybe .8mm thick. Leaving it off won't screw the intake up, but then with the cut skirt you probably went over the edge. Just buy another piston. Your compression is probably near ideal now. Did you use any sealant at the bottom and top of cylinder?
If your clutch pads need cleaning then they can cause drag and affect idling while clutching downhill.

 

[Fletch]

Thanks Jaguar,

I used Indian Head Gasket Shellac on both the base and head. That stuff is messy as all ****, but it does a great job sealing.

I was really hoping I wouldn't have to switch the piston out, but your probably right that it would be a good idea to get some lower torque back. My pipe is tuned to about 3/4 throttle and WOT doesn't add much.

If I change the piston, will that affect air/fuel? I just got finished adjusting my carb and sealing the top shut because the threads are stripped.

I just put in new (used) pads from a broken down engine and I had to jam them in the slots with a screwdriver. The pads that were there were completely flat and red colored. No weave in them at all just solid material...almost like clay, and they had wiggle room in the slots.