Did I hone too much?

[Guest]

I did the top and bottom end of my Katana 750 last year. Took the head off because of some leaking intake valves. Now I am wondering about the pistons and cylinders. I guess I put maybe 2-3000 kms on it since the rebuild. Looks like theres more carbon on the pistons than there should be. Partly I attribute that to the cheap ebay valve seals I used last time, the backs of some of the intake valves had carbon deposits on the them. I paid over $100 this time for genuine Suzuki seals this time. I never noticed and blue out the pipe or using any oil. I honed it with a 240 grit hone and new rings. Should have been a 320 grit from what I read. I checked compression before taking the top end off and was getting 150 psi cold after 6 or 7 compression cycles. It really should hit max psi after 4 or 5 compression cycles. I have good spare cylinders and pistons on hand. I cant decide whether to go ahead and install the spare cylinders and pistons or just run it. I would hate to have to tear it apart again for some reason. I am indecisive and need some input.
Thanks






Heres a pic of what I did to the head while I was replacing some intake valves:

[GregT]

Did you check the ring side clearance in the grooves ? Too much will negate fitting good rings and give symptoms like you describe.
Did you hone full stroke of the cylinders ? looking at the pics it doesn't look like you've honed to the top...
Running in - synthetic or mineral oil ? These run very light ring to bore pressures and full synthetic on fresh bores can glaze up quite easily.
Shortening valve guides on a road motor won't gain you much HP...

[Nessism]

150 psi cold is good. Carbon build up on backside of valves and piston top is normal.

240 grit hone is fine. I prefer more roughness instead of less, particularly on a used cylinder.

The viton valve stem seals as sold on ebay have a decent reputation. Tons of guys on KZ Rider swear by them but of course, stock is fine too.

[DohcBikes]

Your crosshatch is way too flat and it does appear to be too deep. It should not be nearly as visible as it is after 3000km.

The flat crosshatch will cause a film to build and the rings will never seat properly.

Ring to bore pressure is NOT what seats rings. Cylinder pressure under load is what seats the rings.

Your 'porting' job will likely show a loss in power on a dyno and your valve stems will now wear at a much faster rate.

If you don't own a flow bench you really shouldnt be porting anything. Obviously there are exceptions for proven techniques that have been track tested time and again, but porting is a very complicated science. You can gain flow and lose power. A porter that is worth his salt will sometimes add as much material as he removes.

Did you measure ring gap before installing them?

Exactly what oil are you using?

What was your break in procedure? Specifics are neccessary if you want to enter that discussion.

If it were me, I'd start all over and do it correctly. Please don't take any of this personally they are just facts.

[Nessism]

Your crosshatch is way too flat and it does appear to be too deep. It should not be nearly as visible as it is after 3000km.

The flat crosshatch will cause a film to build and the rings will never seat properly.

Ring to bore pressure is NOT what seats rings. Cylinder pressure under load is what seats the rings.

Your 'porting' job will likely show a loss in power on a dyno and your valve stems will now wear at a much faster rate.

If you don't own a flow bench you really shouldnt be porting anything. Obviously there are exceptions for proven techniques that have been track tested time and again, but porting is a very complicated science. You can gain flow and lose power. A porter that is worth his salt will sometimes add as much material as he removes.

Did you measure ring gap before installing them?

Exactly what oil are you using?

What was your break in procedure? Specifics are neccessary if you want to enter that discussion.

If it were me, I'd start all over and do it correctly. Please don't take any of this personally they are just facts.

150 psi across the board COLD, and the sky is falling? Are you joking?

[gearhead13]

I wish I had taken notes when I did the compression tests. I never noticed any difference between cold and warm/hot compression numbers. I never got over ~120 psi after 4 or 5 compression strokes even before the re-ring. I never had to go any more strokes to get max compression on any other engine. At some point I added oil and probably the 150 or so was with oil in the cylinders and 7 or 8 compression strokes. I also hooked up my compressor to the cylinders and thats how I found that some intake valves were leaking. I was run in with dino oil and with lots of throttle although it wouldnt take full throttle until 8k rpms. The needle was rich which is a condition I have been fighting for quite some time, tried facroty pro and dynojet kits. I never saw so much carbon on the pistons and top of the bores aith so little mileage. Whether it is a over rich condition or oil I dont know how to tell.
I dont know why I included a pic of the intake port. But this thing doesnt make any decent power until 8k rpm to redline, it is a short stroke 750 that never had or will have any low end torque, might as well enhance what it has.

[DohcBikes]

Already has no low end torque and you made the intake ports bigger.

Well, that's a new one for me.

You can't possibly know if you gained anything up top unless you run it on a dyno or a drag track before and after the port mod. Anyone that says otherwise is incorrect.

Almost guaranteed, you did not gain anything but almost surely lost power at all rpm. The only reason to port anything that aggressively is if you have the block built to the hilt.

Oh well. Best not think too deeply on this one. Good luck in the future.

[tkent02]

The needle was rich which is a condition I have been fighting for quite some time, tried facroty pro and dynojet kits. I never saw so much carbon on the pistons and top of the bores aith so little mileage. Whether it is a over rich condition or oil I dont know how to tell.

Running really rich will carbon things up really fast. Tune it better and try again. Carbon in combustion chambers is similar to color on spark plugs, it comes and goes depending on conditions inside the engine. This is why modern fuel injected engines have little or no carbon, they run just about perfectly all the time unless there is a problem. Carbureted engines usually have more, since they don't run perfectly all the time. There is usually a little extra fuel going in under certain conditions unless they are incredibly well tuned which most owner modified engines are not. Both of those kits are not just bolt ons, they tend to err on the rich side because too lean will burn valves, not good when selling kits to customers who in some cases know absolutely nothing about tuning. They need a little fine tuning to be right.

A little carbon hurts nothing unless there is so much it causes detonation, which is pretty hard to get if you are that rich.

I don't know much about porting but from what I've read I think Mr. DohcBikes is probably correct on that.

[gearhead13]

Already has no low end torque and you made the intake ports bigger.

Well, that's a new one for me.

You can't possibly know if you gained anything up top unless you run it on a dyno or a drag track before and after the port mod. Anyone that says otherwise is incorrect.

Almost guaranteed, you did not gain anything but almost surely lost power at all rpm. The only reason to port anything that aggressively is if you have the block built to the hilt.

Oh well. Best not think too deeply on this one. Good luck in the future.

I didnt make the ports any bigger, just removed an obstruction to flow. An engine is an air pump the more air you can pump through it the more power you make, simple.
Flushing the guides is worth 3-5 cfm:

http://www.thegsresources.com/_forum/showthread.php?141735-Intake-porting&highlight=cutting+valve+guides

10 posts on here and you are a self proclaimed know it all? Take your negativity about my porting somewhere else.

[DohcBikes]

I didnt make the ports any bigger, just removed an obstruction to flow. An engine is an air pump the more air you can pump through it the more power you make.

Not If you decrease efficiency/velocity/atomization.

No negativity here. Just telling you what I know to be true. I also did not say that I know definitively whether you lost or gained power. What I'm saying is that in my experience what I see there will not gain power as a stand alone mod. I can understand if you disagree.

[tatu]

Not If you decrease efficiency/velocity/atomization.

No negativity here. Just telling you what I know to be true. I also did not say that I know definitively whether you lost or gained power. What I'm saying is that in my experience what I see there will not gain power as a stand alone mod. I can understand if you disagree.

Surely if only the blunt edges have been sharpend up in order to make the flow more dynamic then the atomised fuel will not condensate when it strikes the blunt faces and gasket matching of the ports would help or put another way the carb stubs where they mount the head often there is ally restricting that orifice which causes fuel to condensate?

[DohcBikes]

Well, I'd be happy to step out if the quoted replies would stop, but since you asked I don't want to be rude and ignore you.

Those intake ports HAVE been enlarged. And smoothed. And the bridge is not straight.

Increasing velocity is the way to gain power on those heads.

From what I can see there it is fairly evident that you will lose velocity. The flushing of the valve guides aided in this. And it WILL make your stems wear faster. For no gain.

Raising the floor of the port as should have been done would negate the need for the guide work.

Katana 750 ports are widely known by racers to be too large to create the velocity neccessary to make peak power.

There is a reason the manufacturers do this kind of thing. (leave the ports too big)

Yoshimura fills their Katana 750 intake ports with epoxy. Their engines are built quite well, from what I have heard.

Do you think yoshimura spends much time below 8k rpm?

And do you think if they did, they would want to see a loss in power in that range?

You don't have to trust me. Email Yoshi and ask them about it.

90% of power that is gained through port work is gained within one inch of the valve seat, including the seat itself.

One of the best ways to guarantee a power gain on almost any head that is bolted to an otherwise mostly stock engine is to have a 5 angle valve job done and backcut the valves. This way you increase flow without losing velocity.

I will add that I have completed over 300 dyno runs as rider and the operator of the dyno to compare the effects of air intake requirements on many different engines. We also had a flow bench to correlate flow gained from porting techniques to gains or losses in power.

Enjoy your afternoon.

[gearhead13]

I was looking over my spare cylinders closely and found this. What would cause this? Is it junk?



DSCF3144b.jpg

[Nessism]

Looks like rust pitting.

[gearhead13]

Thats what I thought at first, but there is no other signs of rust anywhere.