KA100 - X30 honing torque plates

Hi Guy’s, Question for the engine rebuilders on KP.
I’m looking at rebuilding my sons KA100 & X30 myself and am after some advice if I should or need to use torque plates on the cylinder while honing the cylinder to replicate the tension when cylinder is torqued to the correct tensions.
Does anyone know if the professional engine rebuilders use torque plates when honing.

There is none in Sweden who uses torque plates when honing X30s :grin:

Sunnen honing machine is very popular to use


I’ve seen plenty of American builders use torque plates on X30 cylinders. I would assume the same to be true for the KA.

All the ones I’ve seen (mostly Italy) use a small Sunnen like Lucas was referring to, holding the cylinder by hand, no TP. There are very good reasons why. Personally, I’m with the “no torque plate” party

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“No Torque Plate Party”, Why? Virtually all engine builders that I know including myself always use torque plates.
What do you see as the difference?

All based on empirical evidence. I can just tell you my approach, for what is worth.

Take a cylinder, mount it on a empty case (no crank). Torque it down evenly using lube, multiple steps, the best torque wrench you have, the whole nine yards. Now measure it with a good bore gauge and you’ll see you have some deformation compared to prior non-torque state. Undo the bolts and torque it down again, you will see a different deformation. Keep trying, you will always get to a point that is difficult to replicate/predict.
Once it heats up, it will deform in a different way altogether (cold side vs hot side),fastener stretch, etc etc which you can’t measure anyways so it’s just a guess.
So I really think the best bet is to hone it straight from cold with no torque plate, doing whatever you can to then torque it evenly during assembly.
My theory is that if you try to control it via torque plate, you may end up further off as tolerances may all pile up in the wrong direction when installed. They also may all go in the right direction, who knows. Since you can’t control them, I prefer going neutral.

Hope it makes somewhat sense. In a 4 stroke, especially if it’s a car with a big block of metal and torqued down with proper bolts and high torque values, then plates are the way to go. 2 stroke is a different thing.

I’m sure there are two different philosophies here and maybe we are just splitting hairs

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The reason why I asked is most engine builders I know in the past on the old Yamaha 100 J’s & KT’s always used torque plates when honing, but when I ask around about using them on X30’s & KA’s I haven’t found any that use them on these engines and I was wondering why?
Andy you make a lot of sense as when the metal heats up, it could be all over the show.
I suppose that’s why an engine requires a reasonable amount of piston to bore clearance?
How much bore clearance should I use to get best performance?
This might be a stupid question but does the piston clearance play much of a part in the compression of the engine or is only the ring that makes the compression?
Very interesting subject to see what others do and there thoughts on it.
Thanks for all the reply’s

0.14mm seems to be the best performing in X30 engines from my understanding. That is also what I drove with when I raced X30

The manual states 0.11-0.12mm

Thats interesting Lucas as it is a bit more clearance than stand, would you think that would be ok for the KA100 engine as well. By having more piston to bore clearance will the engine have lower the compression ?

Hmm I don’t know if it would apply to the KA100. I have never worked with that engine.

I don’t think you will miss out on compression, I haven’t noticed any change in compression between 0.12 and 0.14. Rings also seal :grin: Get the ring gap proper and you are good to go. Squish near 1-1.1mm

Some nice reading on the KA100: KA piston sizing — Fox + Son Karting

That’s a very interesting thought process, and indeed we may be splitting hairs. In the past I’ve measured torque plate vs. no torque plate and observed the differences but never tried it repeatedly.
I was taught using torque plates and never questioned it again.
Everything you say makes as much sense as anything else so there we are.

If someone were to want to experiment, here is one way:

Take a cylinder, install a torque plate and remove and replace each time between steps:
-start with a boring bar
-hone with a coarse stone, but not enough entirely remove the boring evidence
-hone with successively finer stones, never completely removing the prior finish evidence of coarser stones

What pattern you end up with might tell you if torque plate inconsistency is a thing. I don’t know the answer, but experimentally, you should be able to see this evidence without measurements.

When I asked this question I didn’t realise it could & is such a complex question due to the variables but Andy makes very valid points on the variables he points out that might be in play here.
Another way of testing might be to test with & without TP on the bench then run engine to race temperature at track or on a DYNO then remove cylinder and take measurements again with & without Torque plates and get some comparisons.
No doubt someone a lot clever than me has probably done experimental tests to determine if torque plates are beneficial or not.
Hopefully someone might share there results😉 and reasons for it.

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I’m wondering with such high rpms whether some of the 4-stroke big engine stuff doesn’t apply as much to these 2-stoke zingers, if there’s just not enough time during the cycles for as much loss of compression and combustion pressures. I wish I had time and money to “waste” on research.

ahah absolutely! These are fascinating subjects, I bet different tuners have different approaches and 'secrets" and it’s all good, shows how many variables and possibilities there are.