are kenig hi comp.pistons any good ??

[teazer]

And let's not forget that 98 Octane in the US is (R+M)/2 and not the way it's measured/labeled in the land of Oz.

[nander]

Here's a photo of a kenig piston my buddy pulled out of his bike today. He had seized the motor several months ago and replaced the stock pistons with these. Now it's grenaded again. That ring is actually the top of the cylinder sleeve.

Now, in fairness, he commutes on the bike 60 miles a day on L.A. freeways. That means he is either splitting lanes through jammed traffic or trying to keep up with 75+ mph speeds when it's not. So, that poor little motor was being seriously pushed.

However, when he showed me the huge crown on those kenigs, I wondered whether increasing the compression in an otherwise stock CB77 was a good idea. Bill silver seems to say over and over that detonation is a frequent cause of engine failure, and raising the compression seems like it would increase the likelihood of detonation.

I wonder too if the gas available today just doesn't have the octane it used to, further increasing the risk of preignition. High comp pistons + not particularly high octane gas seems like a recipe for disaster. Here in California, the best we get is 91 (although I've heard there are a few stations here in L.A. that carry Fuelman racing gas -- something like 106 octane!).

[flathead]

Something just occurred to me about the problems with the Kenig Pistons.
The last few sets that I bought were S2's. They came from an EBAY vendor who was out of the proper size rings. He was supplying them with S12 rings and suggested that you grind the ring ends to fit. I didn't think that too good of and idea so I bought up enough proper size OEM rings to do the sets that I had in stock and discarded the S12's. Is it possible the Kenigs that failed were from the same vendor and installed using the "just grind the ends" method? Looks to me that the excessive force of a 2-1/2 mm too big diameter set of rings, even if you could get them to fit in the bore, would heat up and be a recipe for disaster. Just my thoughts. Knock on wood the ones that I'm running and always WFO and with 91 octane "pump gas", haven't shown any problem yet. I had the head off to fix a head gasket oil leak just after breakin and everything looked good. I'm confident enough with them that I'm gonna use them in my next two flattrack bikes, another twingle and a Type I.
But FWIW I've not used them in a street bike and really don't see an advantage there.

Mark

[onemangang]

I bought some Kenig Hi-Compression pistons of ebay and as the supplier noted the rings were to big. I bought .75 over pistons and had some NOS .75 rings handy to use with the pistons. The pistons needed to be altered in order to work properly. They did not fit on the wrist pin proprerly so they could move freely. So a bit of honing was required, but minimal. They also did not have space for the circlips, so a notch was made to utilize the circlips. I believe there was a spot on the piston were the ring was pinched a bit tight from the forging process, so that tight spot had to be sanded down on one of the pistons. It was very minimal. I did not have any clearence issues and have new valves and springs. I am not a mechanic nor did I do any of this work, but I was there for the build and watched the mechanic go through each and every step. He walked me through the whole process and explained what was wrong with the pistons, and I watched him alter them to make them right. He has been building these Superhawks and Scramblers out of the the crates sice the sixties, so if it wasn't for his percision and expertise, I would be driving a time bomb. I have not had any problems with running the engine because of his expertise. I just wanted to post this info in case any one of you are looking to purchase a set of kenig hi-compression pistons, maybe it could be a help to your 305 build. As for now I have one fire breathing Scrambler and am happy with the kenig pistons thus far.

[LOUD MOUSE]

They did not fit on the wrist pin proprerly so they could move freely

Do they actually need to do this?. .................lm

I bought some Kenig Hi-Compression pistons of ebay and as the supplier noted the rings were to big. I bought .75 over pistons and had some NOS .75 rings handy to use with the pistons. The pistons needed to be altered in order to work properly. They did not fit on the wrist pin proprerly so they could move freely. So a bit of honing was required, but minimal. They also did not have space for the circlips, so a notch was made to utilize the circlips. I believe there was a spot on the piston were the ring was pinched a bit tight from the forging process, so that tight spot had to be sanded down on one of the pistons. It was very minimal. I did not have any clearence issues and have new valves and springs. I am not a mechanic nor did I do any of this work, but I was there for the build and watched the mechanic go through each and every step. He walked me through the whole process and explained what was wrong with the pistons, and I watched him alter them to make them right. He has been building these Superhawks and Scramblers out of the the crates sice the sixties, so if it wasn't for his percision and expertise, I would be driving a time bomb. I have not had any problems with running the engine because of his expertise. I just wanted to post this info in case any one of you are looking to purchase a set of kenig hi-compression pistons, maybe it could be a help to your 305 build. As for now I have one fire breathing Scrambler and am happy with the kenig pistons thus far.

[onemangang]

As I stated earlier, I am not a mechanic. The wrist pin would not fit into the piston without honing. I suppose they could have been pressed in with some force, but that would not allowed the pistion to rock back and forth. I guess that would be a bad thing , but truth be told I dont know. I am no expert!
I am merely reciting what I can recall from memory, and truth be told I don't know the intricacy of how everything is suppose to work in the first place. So I may have misunderstood what was being told to me. As this post has coveredalready, there are other options and avenues of travel that are viable. The Kenig pistons are one of these options, just doulble check everything before installing. I am merely trying to give people a heads up on what to look for with the little knowledge that I have been bequeathed! LM Maybe you could expand and point out any misinformation that I may have put out there due to my mechanical shortcommings, to ensure the mechanical integrity of these motorcycles and this forum, being that you have a working knowledge of these engines! Thank you and God bless!

[LOUD MOUSE]

I go by lm not LM unless I want your attention.
Maybe ya can ask your MECHANIC why he told ya the pin needs to move freely?/rock back and forth? in the piston.
Ya the one with the message I questioned not me. ..............lm

As I stated earlier, I am not a mechanic. The wrist pin would not fit into the piston without honing. I suppose they could have been pressed in with some force, but that would not allowed the pistion to rock back and forth. I guess that would be a bad thing , but truth be told I dont know. I am no expert!
I am merely reciting what I can recall from memory, and truth be told I don't know the intricacy of how everything is suppose to work in the first place. So I may have misunderstood what was being told to me. As this post has coveredalready, there are other options and avenues of travel that are viable. The Kenig pistons are one of these options, just doulble check everything before installing. I am merely trying to give people a heads up on what to look for with the little knowledge that I have been bequeathed! LM Maybe you could expand and point out any misinformation that I may have put out there due to my mechanical shortcommings, to ensure the mechanical integrity of these motorcycles and this forum, being that you have a working knowledge of these engines! Thank you and God bless!