Hello from a new ACE 100 Owner!

[Tether]

Or from this to this

[hodakahunter]

Nice work Tether!

[Tether]

Thank you Hunter. That was my first Hodaka. I got a lot of good advice here while building it. I am now hooked on Hodakas and now own 4. There is something special about Hodaka and the people that own them.

[hodakahunter]

Alright, so what do we think? Looks like something got smacked around and eventually blown out. New piston and head? Buff it out ? Cylinder walls look clean. No sign of whatever the pinballed object was scoring the wall.

[matt glascock]

The repeating circular pattern on the piston crown suggests shattered ring. I don't see any deal breakers yet. How does the bore and wall of the piston look? Piston/cylinder clearance?

[hodakahunter]

I didn’t notice the pattern in the shape, but that makes sense. Rings are in one piece so this likely occurred and then new rings installed. Will need to check the clearance tomorrow.

Bore and walls look clean. Can still see the hone.

So this deformation doesn’t lead to stress fracturing or the small volumes of gouged material causing heat retention and detonation? I shouldn’t replace it while I’m in here?

[thrownchain]

I'd say go with a new piston. The head I would smooth the edges on the divots and use it.

[hodakahunter]

I'd feel better if it were replaced.

I may have a lead on a Webco head and piston. Wondering if this would be something I should tackle in my first build, or just try to keep everything stock. Hmmmmmmm...

[matt glascock]

Again, it depends on what you intend to do with the bike ultimately. Also, it depends on the size of the piston. If the cylinder wall looks good, would clean up with a light hone, and is on its standard bore, it would be unnecessary to give it a 3rd overbore just to fit a sexy piston. Most of the Webco parts I'm familiar with were performance oriented for hop-up application. I'm with Thrown. Clean up the head and get a new properly sized piston. Just a thought. Here's what I'd do. Carefully pack up the cylinder and get it to Hodaka Dave. He does shop work with Terry Larson at Hodaka_Parts. For $220, he will clean up the cylinder bore, over bore if necessary, and properly fit a brand new piston kit. While $220 is a sizeable investment, in the lung run, I'd say its a darn good deal for a bolt-on-and-go spec top-end.

[viclioce]

Matt is right. Heck, it costs me $120-35 for a new piston, $25-40 for a set of rings & $40 for a local machinist to hone & fut. So the only diff is postage and a Hodaka Dave set up will be worth GOLD!!! Victor

[hodakahunter]

Update on the Ace...

Cases are split. Assessment so far is that it was running a +.040" piston (1.966 at the skirt) and bore is 1.973, which gives a total bore clearance of .007", so based on the .003-.004" acceptable clearance specs from the workshop manual I received, she's worn slap out with no chance for another bore.

Is this a fair assesment of the situation based on the numbers?

Going after the crank next, but not expecting much if there was this much wear in the cylinder.

Will keep you updated.

[matt glascock]

If you think about it, that dog won't hunt. You might squeak out another overbore, but the durability would likely be horrible. It would probably overheat the first time you rode it for more than 15 minutes. The expense of an overbore and piston kit would likely not get you far down the road. Used cylinders are plentiful and surprisingly inexpensive. Start with a good, serviceable jug with a fresh bore and piston and get yourself some mileage on that sweet Ace.
0.00000000002

[hodakahunter]

Matt,

Thanks for the confirmation. Guessing that the previous owners really got their money's worth out of this motor. Good to see, really.

What would your opinion be on trying to build up a super rat setup in this bike? Cylinder, head, ported pistons, reeds, 24mm carb etc.? From everything I've read and been told it is compatible and should give a bit better power while not making it unreliable. On this point, I've found it difficult to find Super Rat components (Ebay mainly) lots of Wombat and Ace, but very little Super Rat. Is the best source of parts within the Hodaka network and not through Ebay? Just trying to get an accurate picture of parts availability when you say that they are "plentiful and surprisingly inexpensive". Assuming that you were referring to replacing Ace components of course.

As you might be able to tell, I'm not that interested in restoration. More of a resto-mod kind of guy I like old stuff with a punch!

[thrownchain]

Lots of "stock" Ace stuff out there. If you're gonna uprate your motor it shouldn't be a big deal. The parts hunt can be the best part of the trip.

[matt glascock]

Hodaka Dave can build you up a Super Rat motor to your specs that will be a bolt and go unit.

[hodakahunter]

Doh!

It would help if I looked at the ACE 100 SUPPLEMENT section of my Workshop Manual. Different story all together now!

This would now be an original piston with significant wear -.010”!

Need to reassess what might happen next now.

Still might work on a hopped up top end arrangement, but will now consider just getting this cylinder clean and back in service.

[matt glascock]

Great News!!!

[Al Harpster]

There have been extensive discussions about piston/cylinder fits on this site.

And here's my take, for what it's worth.

It's damned hard to check a cylinder that's got port holes in it with a dial bore Gage. If you're talking one with boost ports it's even worse.

If you try telescoping bore gages I believe you'll drive yourself crazy because of out of round and taper conditions. The telescope Gage will fit one place, won't fit properly in another.

Get a set of feeler gages with the screw in the "hinge" part. Take it apart and start putting feelers between the piston skirt and cylinder when the piston's in it.

You get an .005 or .006 feeler Gage in, you're probably pushing the limits pretty hard.

This will give you an initial evaluation.

Where you go from there..... Depends on what you want from the engine and your budget.

Bottom line, be careful about what and where you're measuring and how you're measuring it.

You'll get a bunch of numbers, but it's the fit that counts.

[hodakahunter]

Al,

I understand completely now! It took me a while to take enough measurements up and down the bore after getting caught on the ports and having to re-seat the gauge, but I did get consistent 1.985” up and down and at different angles, so fairly confident that this is correct.

The piston is definitely worn. But not sure on what size to order (stock or over). I may be limited by supply since there seems to be a limited quantity of everything but +.040”. Is this due to the other inventory being used up over the years? Or is everyone going to the max overbore for the additional displacement? Seems like we might be cutting short the life of the fixed population of cylinders with this practice.

I should just cut through the guess work and have Dave or Rich do the work for me. I just like knowing the why and how, even though I don’t have the tooling to complete the machine work.

[Al Harpster]

Oversize Pistons often have a marking that's visible on the crown. .25, .50, .75 etcetera. Does your piston have any numbers stamped on the crown?

.25 mm is about .010".

Sticking with the inch system, standard piston is 1.967".( Per the Book, it's 49.96 mm.)

Let's add .003" for original factory clearance. Just for this discussion.

Target bore would then be 1.970.

You find 1.985?

If you trust that number, looks like you're BETWEEN first and second over.

Could be you've got a well worn first size over cylinder. If you buy that.

Far as piston wear: if it's scored big time, maybe.

If not, it's close to on size.

To ACCURATELY measure piston diameter it's 1-2" micrometers. Calipers, I don't like them for piston measuring. Be sure you set the mike to the standards Gage first. Art Pistons are both tapered and oval.

Again, it's the fit you're after. Consider the numbers with grains of salt, but chase the fit.

I wouldn't consider +.040 unless it was the very last resort. Don't think it's necessary.

If you're getting 1.985 CONSISTENTLY you're not getting good measurements. Ain't nothing consistent within .001 on a used cylinder.

That's my two dollars worth. And I own the mike's, the calipers, the dial bore Gage and the professional Lisle cylinder hone. I got hundreds of dollars behind my two dollars worth.

Like you, I wanted to know for myself. So I bought all this stuff.

Look for markings on the crown, use feeler gages to find where you are in the fit neighborhood. If you want piston size use a micrometer and know that the skirt is oval shape.

[hodakahunter]

Al,

Edit *no stamp just an arrow*. Nothing that I would call scoring in the cylinder. Looks like a good hone would remove any marking that is visible.

Bore measurement was using a telescopic gauge calibrated to a 2"-3" mic, that was calibrated to a 2" standard. When I say I consistently measured 1.985", that was consistently the narrowest diameter seen when rocking the gauge, so true perpendicular measurement may deviate from this, but I get what you're saying. Perfectly uniform dimensions rarely exist on wear surfaces, also given that the ports probably disrupt uniform expansion of the bore, the wear should reflect this.

I would agree on the between 1-2 overbore based on the math. Hodaka-parts only sells a +.040" ace 100 piston, so will need to shop around for a +.010. Also, I don't know what kind of life to expect out of it if replacing between two sizes, and if itsn't just worth going up and doubling the wear that can be tolerated until next overhaul.

Quick search on ebay indicates no Ace100 pistons with +.010" or +.020", so that may be my answer right there. Not probable due to scarce availability of parts. So might be better to get a new cylinder, and if doing that, go ahead and put the time and money into a super rat high compression cylinder, head, and piston.

How does this sound?

[Joe Ormonde]

Sometimes a good way to check a cylinder is to put a new ring into the cylinder and measure the end gap checking it in several places taking note of any change. Also, look for light in between the ring and cylinder every time you re-locate the ring. Just this simple test will show a out of round bore. I check all of my Cylinders with a ring. Joe Ormonde.

[Al Harpster]

Joe's ring test conducted with care can tell you more. Especially about out of round.

First, I'll assume you asked directly about availability of, say, a plus .020 Ace piston. Maybe there's something not shown on the site. Strictly Hodaka had some made, maybe there's one left in the last tranfer. Maybe an .030.

But, you can consider the "model 92" Super Rat Pistons on offer. Then ask for the corresponding ring.

Add to that "ask" a good used rat head to match.

Swap to the rat piston and head.

I'm not crazy about measuring less than 2" with a 2" mike, but okay. I get it.

Then, if your really, really sure you're at 1.985 maximum condition it's possible to hone up to the plus .020 piston. But the numbers you have still sound strange to me.

What is the LARGEST dimension you Mike at the end of the piston skirt?

I'm guessing you're at $200 for the parts I'm talking about here, plus shipping. Probably more.

You have access to mikes, standards and telescoping gages. Want to dive in, buy the Lisle cylinder hone and do it?.

The hone may go small enough to do your YL1.

[dirty_rat]

If you are on FaceBook, there is a Hodaka group on there. Recently someone posted that they had some Hodaka pistons and rings for sale. You might check there for what you need.

[hodakahunter]

Dirty Rat,

Thanks. Not sure where a majority of the Hodaka crowd is for advice and sourcing between FB and here. This seems to be better for hashing out technical details. Will post to the Hodaka Fan Club group for parts needed.

I need to get out of my "catalog" mentality of "If hodaka-parts doesn't have it, tough luck." Far from the truth I'm sure thanks to a great network of owners and enthusiasts on here!