Topic: Cheap 836 kits back on ebay...$110! *Update!

[KJ790]

Did you not see this, i sent a copy of the reply to Matt.. I'll happily get my info from guys i trust and respect.  You are the only guy i have seen on the forum that endorses the use of K model pistons in a late model F bike...

You must not have seen this then:

I've built a couple engines with similar parts, lately. A couple of things to think about:
1. The piston clearance on the forged Wisecos is more than on the cast pistons: about 0.0018"-0.0022" because of the differing materials. This means they will always sound a little "slappy" when cold, and act slightly tight when the engine is first started up warm (not hot) after it was fully warmed, then parked a while (because these pistons cool slower than the fins and liners). So, don't fire it up warm and rap it up tight: give it a minute or two for the heats to rematch first. If you don't, over time it will scuff the wide sides of the piston skirts and start damaging the rings. This has always been the hallmark of forged pistons in these engines, when not run "just so" in daily riding. (I hope this doesn't start an argument...)
2. Those Wisecos work fine in the "K" engines as 10.25:1 compression with the stock cam, unless you also add a quench band around the circumference of the chambers to match the bores: then it comes down to about 10.1:1. With the "F" engines and that stock cam, they come in at about 10.1:1 compression without quench and 10:1 with quench bands. With the #41 Webcam, it drops to about 9.7:1 because of the excessive overlap of that cam. In any case, the compression goes WAY up, because the bores are so much larger than stock while the chamber remains the same size. Even the flat-topped 836cc (65mm) "cheapie" pistons raise the compression ratio to almost 9.5:1 with the stock cams in the "K" engines (150 PSI test pressures).

There's lots of people running 836 kits for K model engines with F2-F3 heads. Anyone that says it does not work simply has not tried it. As I said before, I already posted comparison pictures of the pistons as well as actual measurements. My information seems to agree pretty closely to Hondaman's information from the past. I know that Hondaman is pretty well respected around here so I think people are going to believe him more than your anonymous mechanic friend who couldn't give any sort of numbers to back up his reasoning.

Please stop posting misinformation based on rumor and hearsay and please stop trying to turn this into a pissing match like a child.

[fatmatt650]

Let me just throw this out there. -
836/4 = 209cc / cylinder
27cc combustion chamber volume in the f2/3 head (as quoted by KJ, can anyone verify this?)
209/27 = 7.74:1 compression ratio with "flat topped" pistons

I doubt it's as simple as this though. According to my own crude calculations the domes in the stock pistons would have to take up 59cc of space each to give the claimed stock 9.0:1 compression ratio and they don't look like they are that big.
Any one wanna bust out the slide rule and give us some definitive information?

[KJ790]

Let me just throw this out there. -
836/4 = 209cc / cylinder
27cc combustion chamber volume in the f2/3 head (as quoted by KJ, can anyone verify this?)
209/27 = 7.74:1 compression ratio with "flat topped" pistons

I doubt it's as simple as this though. According to my own crude calculations the domes in the stock pistons would have to take up 59cc of space each to give the claimed stock 9.0:1 compression ratio and they don't look like they are that big.
Any one wanna bust out the slide rule and give us some definitive information?

You are off a little. Static compression ratio is the volume at BDC divided by the volume at TDC. The volume at BDC is the displacement (209cc) plus the combustion chamber volume. The volume at TDC is just the combustion chamber volume. So if the combustion chamber is 27cc, the compression ratio is (209+27)/27 which equals 8.74:1.

Another note, contrary to popular belief, the ebay pistons are not actually flat across the top. They appear to be flat but really have a 1.5mm dome shape to them. This is a smaller dome than the stock F2-F3 pistons however, as you could see in the picture I posted earlier.

[fatmatt650]

I'm using a CR calculator at - http://www.csgnetwork.com/compcalc.html
These are the numbers I'm putting in -

Enter Bore/Stroke Designation Type
1 = Inches 2 = Millimeters     
Enter Cylinder Bore Size      - 65
Enter Piston Stroke Length - 63    
Enter Head Gasket Bore Diameter - 65   
Enter Compressed Head Gasket Thickness - .030 (assuming mls gasket from cycle-x, is this listed in inches or millimeters? Cycle-x doesn't say)    
Enter Combustion Chamber Volume In CCs    - 27
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') - 0
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') :  - 0

KJ - Any idea what the volume of those mini domes might be? Also, where do you get the 27cc from?   

[Rigid]

"Sounds like you buy all the trick parts you can and then pay someone to bolt them onto your bike for you."  You nailed that one.  Check a few of his posts, he is proud of his lack of hands on knowledge.

[Radam]

Sorry guys, but this is all I can think about when I read this thread anymore.

[Rigid]

Priceless..............

[KJ790]

I'm using a CR calculator at - http://www.csgnetwork.com/compcalc.html
These are the numbers I'm putting in -

Enter Bore/Stroke Designation Type
1 = Inches 2 = Millimeters     
Enter Cylinder Bore Size      - 65
Enter Piston Stroke Length - 63    
Enter Head Gasket Bore Diameter - 65   
Enter Compressed Head Gasket Thickness - .030 (assuming mls gasket from cycle-x, is this listed in inches or millimeters? Cycle-x doesn't say)    
Enter Combustion Chamber Volume In CCs    - 27
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') - 0
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') :  - 0

KJ - Any idea what the volume of those mini domes might be? Also, where do you get the 27cc from?

The 27cc approximation was my measurement taking everything into consideration. The dome of the ebay piston is about 3.25cc, the head gasket volume for an .040" thick gasket is 3.37cc, the dish in the head is 27cc. This gives you a total combustion chamber volume of approximately 27.12cc. If you go with the .030" thick head gasket then your gasket volume decreases to 2.53cc, so your final combustion chamber would be 26.28cc.

The thing to understand is that changing the static compression ratio alone really does not have as significant of an effect as some would like you to believe. According to the chart in David Vizzard's book "How To Build Horsepower", changing the compression ratio from 9:1 to 10.5:1 will give you less than a 2% power increase. That equates to around a 1hp difference on these bikes. So as I have said from the start, if you are trying to build the fastest engine possible then obviously go with the higher compression pistons. However, if you are trying to get more power on a budget then these ebay pistons are nice since they will save you over $250 and give you 9/10 of the power gain of the higher compression pistons.

[KJ790]

Sorry guys, but this is all I can think about when I read this thread anymore.

Haha classic!

[Retro Rocket]

Please stop posting misinformation based on rumor and hearsay and please stop trying to turn this into a pissing match like a child.

Misinformation..?  So now you are saying that the F2-3 pistons are not different.? You are saying that using K pistons will NOT result in a drop in compression. You are kidding right.....

There's lots of people running 836 kits for K model engines with F2-F3 heads.

Yes, with mods to the heads to make it all work, otherwise they leak oil. Why bother doing things the more complicated way when its easily done with the correct parts...? {which has been my point from the start}

I just love this habit of calling people names because you disagree with what someone else says, really says a lot to me about your lack of ability to discuss something without being an ass . I now suppose you will tell us all that Weisco and others are wrong for making different pistons for the F models, including Honda?  You obviously don't think 8.? to 1 is low compression, i disagree....   The thing is, i don't give a stuff what you use, Matt wants something from his engine that can be easily achieved by using the correct parts , your method is to walk all the way round the neighbor hood just to cross the road, buying cheap cast pistons {weisco are forged} then using expensive gaskets and other mods that are unnecessary if you use the right parts. I never said it won't work, it is just a round about way to achieve less performance that you will get with the cheap cast pistons. Matt could simply put the correct pistons with the gaskets supplied with the kit and be done with it, and still have better numbers than he would have with the lower comp pistons, Why do you think thats misinformation...?
Most guys here do not build their own engines so my approach would be to inform people to do things the correct way which in this case, is much easier and less complicated. If you have all the gear and like playing with, and modding things to suit, then good luck to you. The main thing that will determine where Matt would like his torque curve to be will be the cam....  By the way, Jay from APE engineering said that you will also get lower compression with pistons meant for a K model, thats good enough for me....

[Roach Carver]

We could solve this whole problem if someone would jsut give him an old K engine.

[Retro Rocket]

"Sounds like you buy all the trick parts you can and then pay someone to bolt them onto your bike for you."  You nailed that one.  Check a few of his posts, he is proud of his lack of hands on knowledge.

Thats great coming from someone with the credibility of a crack whore.....  You know, you would have to be one of the most mindless idiots i have ever come across. You follow me round this forum like a complete moron spewing crap with absolutely nothing to do with anything within the thread, that says heaps about the person you are King, nothing new here at all.

[KJ790]

Misinformation..?  So now you are saying that the F2-3 pistons are not different.? You are saying that using K pistons will NOT result in a drop in compression. You are kidding right.....

Read my previous posts. I have already addressed everything here. I have pointed out all of the times you stated something that was not accurate and gave you the actual facts with values to back them up.

Yes, with mods to the heads to make it all work, otherwise they leak oil. Why bother doing things the more complicated way when its easily done with the correct parts...? {which has been my point from the start}

So you're saying that these engines will leak oil if you use the ebay pistons and not if you use the cyclex pistons...  The reason I use these is to save money, as I said from the start. I am not telling anyone to do anything, I am simply saying that it is possible to use these pistons.

I just love this habit of calling people names because you disagree with what someone else says, really says a lot to me about your lack of ability to discuss something without being an ass.

Thats great coming from someone with the credibility of a crack whore.....  You know, you would have to be one of the most mindless idiots i have ever come across. You follow me round this forum like a complete moron spewing crap with absolutely nothing to do with anything within the thread, that says heaps about the person you are

Call the kettle black much? What name did I ever call you?

I now suppose you will tell us all that Weisco and others are wrong for making different pistons for the F models, including Honda?  You obviously don't think 8.? to 1 is low compression, i disagree....   The thing is, i don't give a stuff what you use, Matt wants something from his engine that can be easily achieved by using the correct parts , your method is to walk all the way round the neighbor hood just to cross the road, buying cheap cast pistons {weisco are forged} then using expensive gaskets and other mods that are unnecessary if you use the right parts. I never said it won't work, it is just a round about way to achieve less performance that you will get with the cheap cast pistons. Matt could simply put the correct pistons with the gaskets supplied with the kit and be done with it, and still have better numbers than he would have with the lower comp pistons, Why do you think thats misinformation...?

I never once said such a thing, nor will I ever. Looks like you need to reread everything I have posted.

[fatmatt650]

  You're all a bunch of poopyfaces. 

[dragracer]

Simple question: If i use these cheap Ebay pistons in a motor with a K model head, can i expect any gains in power?

[Retro Rocket]

    Yes, with mods to the heads to make it all work, otherwise they leak oil. Why bother doing things the more complicated way when its easily done with the correct parts...? {which has been my point from the start}


So you're saying that these engines will leak oil if you use the ebay pistons and not if you use the cyclex pistons...  The reason I use these is to save money, as I said from the start. I am not telling anyone to do anything, I am simply saying that it is possible to use these pistons.

Dude, you have some serious comprehension problems, that was in context to using a F2 head on a K model block....   And if you were as smart as you are trying to make out you would know that....

Call the kettle black much? What name did I ever call you?

Unbelievable, that was aimed at KING custom cycles {RIGID} who never adds anything competent to the debate, just petty crap.

trying to turn this into a pissing match like a child.

There you go, next question...

[Retro Rocket]

Instead of being completely argumentative, why not address what i was saying, Why should someone go to all the trouble of doing the things that you do with those cheap pistons, to make them work in a "F" model engine when, for close to the same amount of money and with less time and screwing around, just use the parts that are meant for the F bike. Now if you can stop taking everything out of context and turning this all to #$%*, see if you can give me a straight forward answer....

[fatmatt650]

Because they are comparable in quality to the factory pistons, very inexpensive and keep the compression ration comparable to factory specs.

Retro, if you can add anything to the knowledge base here please do. A more definitive measurement of the f2/3 combustion chamber volume would be helpful.

Once again - I want to increase displacement but keep factory CR. If you are aware of another piston set that accomplishes this, please post a link. If you can point out any mistakes in the CR calculator math, please do. Thanks.

[fatmatt650]

Simple question: If i use these cheap Ebay pistons in a motor with a K model head, can i expect any gains in power?

I heard those pistons suck.

[scottly]

 A more definitive measurement of the f2/3 combustion chamber volume would be helpful.

A definitive measurement of the cheap piston's dome volume, as well as the late F piston dome volume would be very helpful...

[Grnrngr]

So..if I put late model F pistons in my early K motor, will I get really high compression??   

[Roach Carver]

briefly, ha ha ha ha

[HondaMan]

Simple question: If i use these cheap Ebay pistons in a motor with a K model head, can i expect any gains in power?

Yes.
And, if you deshroud the valves and add a quench band, improve the ports, polish the valves, and do it all correctly, you'll be nudging 80 HP at the crank. How much gets to the rear wheel is a topic for a whole book.


...oh, wait.

[srbakker]

Haha

[fatmatt650]

Simple question: If i use these cheap Ebay pistons in a motor with a K model head, can i expect any gains in power?

Yes.
And, if you deshroud the valves and add a quench band, improve the ports, polish the valves, and do it all correctly, you'll be nudging 80 HP at the crank. How much gets to the rear wheel is a topic for a whole book.


...oh, wait.

Care to chime in on the current "debate"? I promise not to call you a poopyhead.