1973 Combat Wombat Top End Specfications

[Buckwheat]

Howdy

I'm working on my first Hodaka. The cylinder is slightly scored and the piston is marked with a 10. I am assuming that it's already been bored out to 0.010 over stock.

So I probably need to bore the cylinder and put in an oversize piston. What are the specifications for the bore oversizes on the 1973 125 Hodaka Combat Wombat. Or maybe I should say what are the bore sizes for 0.10, 0.02, 0.03, 0.04 over bores.

Thanks

[Bert44]

When I’ve built Hodakas I’ve gone for .0045” clearance after heating both barrel and piston and measuring and comparing the expansion rates of both. I built a BSA B44 with a piston (JE) that had a recommendation of .0025”. It worked well for 4000 miles before I sold it. Ive heard of many other Brit bikes that need .006” with the pistons available. A good machine shop should be able to help if you take the new piston and barrel along.

[Dale]

Your assumption is correct that the current piston is .010 over standard.

As for bore sizes it is really risky to just list a fixed size. The cylinder should be custom bored to fit the new piston for the proper clearance. Pistons were originally offered in 4 sizes. .010, .020, .030 and .040. Aftermarket then went up 4 more sizes to .080.

It makes it tough to guess what size piston is needed. For example, if you purchase a .020 piston and then the boring to match it does not clean up the cylinder then you looking for another piston in the next size up. The easiest route is to ship it to a Hodaka specialist and let them choose the correct piston from their inventory and they will bore the cylinder to specs for that piston.

Sorry for the long answer...
Dale

[Dale]

The original spec calls for .003 clearance. This can vary with piston manufacturer and personal preference.

[viclioce]

Send the cylinder to Terry Larson at Hodaka-Parts.com. He will have Hodaka Dave Rosier do the bore and Terry will supply the needed piston assembly. Hodaka Dave is one of the best Hodaka machinists you’ll ever find! Dave will decide based on measurement which oversize the cylinder will need. Victor

[taber hodaka]

Slightly scored can mean many things, Is slightly scored where a slight use of the hone would clean it up? What are the clearence's now? Are you going to restore it or put it in a museum? If you just want allot of fun miles, that can mean different things. I will never bore unless I have to but I do want a tight fitting ring, I file a oversize ring to fit. Bore it when you must, not just when you have extra money.. Aren't NOS rings and pistons hard to find? Just me $.02 worth ______________________ Clarence

[viclioce]

NOS pistons & rings are getting harder to find. But the Wiseco sets Terry is currently offering work very well also! And, according to Bruce, there are some folks out there who have pistons available up to .060 overbore. At least maybe for Aces. So it’s not the critical issue which could be perceived, at least to keep a rider going! Victor

[taber hodaka]

A new set of rings is faster, cheaper, quicker, less freight and could take you thousands of miles, slightly scored might not be a big deal. I'm just thinking of the practical, economical guy or gal that just wants to get some fun riding rather than selling the seat on ebay because it looks too expensive. --------------- Clarence

[viclioce]

Clarence. I agree with you 100%!

However, sometimes we get rings that are rusted in place and no honing is going to remove those scratches. Here is one from an Ace which Alan just had a machinist get “unstuck!” Not much of a choice but boring with scratches like those... Victor