Help me spend $200

[oochaDog]

I need to purchase a new piston assembly and probably a top end rebuild package for my reeded Ace 100 but before I purchase I need to know the difference between the Model 93 and 98 Super Rat reed valve pistons I see on hodaka-parts.com but I can't get a hold of anyone there. Can anyone tell me how to get a hold of someone there? I've tried the number on Facebook, their webpage question form and Facebook messenger but no luck.

Or if you can tell me of different vendors I could contact I'd really appreciate it (strictlyhodaka.com doesn't seem to have this type of piston in stock).

Thanks for any pointers.

And if you're wondering why I need a new piston.. ..

[Bullfrog]

Yup, I think you got ALL the good out of that piston!
Ed

[taber hodaka]

Yes but why and what caused it??-----------Clarence

[hodakamax]

All speculation on the cause. Probably more than one thing. I'm guessing that the piston and/or ring was nearing the end due to excessive clearances and failed at the weakest point from rocking. On a piston with holes in the skirt it can at be the corner (if rectangular) of the lower holes. Usually the skirt breaks off. I looks like the crack started on the upper right corner of the lower hole which is typical. When I blow the picture up it appears the end came when the ring broke and pieces got out into circulation completing the fractures by getting into head space and ports. I see a couple of big dings at the top near the failure. The ring probably broke from excessive wear and flopping in the ring groove. What happened first? I always liked the term the term "massive trauma." It's kinda like looking at a crater where an airplane struck the ground and someone asked what did the pilot die from? Massive trauma.

OK, my guess is that the original cause was excessive clearances. I suppose that if we go back to the making of the holes in the piston the piston could have been cracked by a jamming tool. The chicken or the egg, which came first? Another term I like is catastrophic failure which this one falls into.

Sorry I got carried away in cause and effect but it's what Clarence asked. He's always doing that. Definitely time for a new piston and almost certainly a rebore.

Thanks for listening---

Maxie

[racerclam]

The difference between a 93 piston is that you had to drill your own reed holes and the 98 piston came with them . I don't remember if the 98 piston was thicker like the 97 piston is compared to a combat wombat piston

Rich

[oochaDog]

Thanks for all the input, I really appreciate it.

I now have a couple questions about rebore (I'm a newbie about all this). To me the cylinder looks good but I'm OK if a rebore is needed. These are the broken piston diameters I've recorded
49.69mm
49.78mm
49.76mm
49.79mm

I can fit a .006 feeler gauge between this piston and the cylinder at the top and the bottom, but it's tight, .007 won't fit.

So by my calculations a .010 oversized piston won't fit, but the clearance is bigger than the manual says it should be.

If you guys recommend a rebore with that info what diameter would you rebore to and which oversize piston would you go with? And if it matters my riding is racing vintage MX.

Thanks for you time.
Jay

[hodakamax]

Hey Jay, rebore should done if it doesn't meet the Manual specs. .010 over probably will clean up the bore however if you can't find one, .020 or bigger can be used depending what's available. Clearances will be determined by the qualified person doing the boring. The gang can probably recommend someone to do such things in your area or someone to ship it to. This is rather a vague answer I'm giving and someone who bores engines could give you a more precise answer. They could measure the cylinder and determine precisely what size you need before you buy the piston. Usually steps of .010 relines the bore unless it has been severely damaged.

Max

[oochaDog]

Thanks Max! Yep I'm open to recommendations to qualified people to rebore. I'm in the TriCities, WA area, but could ship it out.

[Hydraulic Jack]

If you took your measurements with the broken piston shown, you really don't know yet whether a rebore is needed, or just a clean up of the cylinder walls. For example, you measured a 0.006" clearance in places up and down the bore, but if you used a piston that itself is worn by 0.005", what really is your bore dimension, and what would be the clearance starting with your bore as it is and a new undamaged piston? Who knows. Your problem will be that you will need to buy a piston to do such a measurement, and if it then needs the next size over rebore, you have a piston you can't use. A machinist who works with Hodaka may have a test piston to use for reference so you get only what you need the first time.

Without looking at the bore, I am going to guess you will need a rebore anyway and go one size over, or will need to have the cylinder plated in order to stay with stock bore, which I think is what you have now. It may be worth your time to find a machinist and send your cylinder there, and let that person sort out which size is needed.

Someone else will have to address the question of whether the newer style model 98 piston actually works on a 93 rod or vice versa. There is a cross reference parts list on the Strictly Hodaka website which may answer the question. The two styles would have to have the same wrist pin diameter and the same crown height, but one model is an iron cylinder and the other an alumiferric cylinder. I would not assume they use the same dimension rod.

[Larry S]

I'm not familiar with "TriCities,Wa". If your in Washington state, Ron Liddle is your man. His contact info can be found on this site.

Larry S.

[racerclam]

yes a 93 and 97 piston will interchange , I thought I mentioned that , The con rod is the same too

Rich

[viclioce]

And by the way, Raserclam (Rich) can do your boring and also can do porting for your motor, if you need someone! He might even have a piston, if you ask. Here's his website! Victor

http://richstaylordporting.com/index.html

[thrownchain]

A couple of things, first you're not going to get accurate measurements from a broken piston. Second, measuring the bore and comparing it to the stock dimensions will get you to which size piston you will need. And third you can not do bore clearances with a feeler gauge. ( not properly)

[taber hodaka]

Well you can sure tell when it is well beyond tolerance or too tight. I know a machine shop would not use the feeler gauge method. Remember you would measure a clean bore not a scored one. ----Clarence

[thrownchain]

True, any scoring would have to be removed by boring to get a true round bore. If the bore is scored your rings won't seat or seal.

[bchappy]

Back on Sept 22 I think Rich meant the 93 and the 98 piston will interchange. The 97 is a 125cc.

[racerclam]

You missed what I said . I know the 97 is a 125. I was saying I don't know if the 98 piston is thicker than a 93 as with the comparison between a Super combat and a combat wombat

Rich

[bchappy]

Rich, you looked back to your Sep 22 comment at 10:22 am. I was referring to your comment Sep 22 at 4:20 pm. The 93 and 97 will not interchange. Just looks like a typo.