Thread: New parts or remachined old Honda parts?

Hi All,

I looking for advice on the benefits / disadvantages of using
remachined original Honda cylinders and head versus buying a package of new parts from one of our internet suppliers. I have an original CT70H engine with several reasonably good cylinders and heads. There is a business on ebay that will do a cylinder for $55 and a head for $80, but after I buy the valves, piston and seals (and not including a new cam), the cost for preserving the originality is higher than starting with new parts with a bearing cam.

So does anyone have an opinion on which engine would perform the best and longest? I like originality, but if the chinese are doing as good of a job, maybe these new parts are smart.

Clark
1970 CT70H

The answer is...it all depends.

OEM Honda parts have the edge in quality and as long as the head/cylinder are sound enough for a rebuild, you can't go wrong. $55 to bore & hone a cylinder is a good price. $80 for a valve job, without valves is high; $50 is more like it, if you're supplying the valves.


The cost of reboring & honing an existing cylinder + piston kit is going to come out nearly the same as the cost of an 88cc bore-up kit. The better bore-up kits have aluminum cylinders w/steel sleeve. If originality is important to you, that's not the hot ticket. The markings are different and the non-stock aluminum casting is easy to spot. Many of the chinese heads have larger ports/valves than OEM Honda CT70 versions. Again, there are some appearance differences. My biggest concern would be with the head. As prices have dropped, so has quality and I've personally seen some real junk. It's buyer beware.


Since these are bolt-ons, not permanent mods, you probably should decide whether you're after all-original or performance. Stock will last the longest and look "right". If you're after performance, then I'd go for an 88cc kit and quality performance head from a known manufacturer. You'll also want a hotter cam, better exhaust, angled intake manifold and 18mm carb. An external oil cooler should be added, as well. The middle ground would be porting an OEM head and adding a hotter cam.

Hi RacerX,

I appreciate you responding. I am basically recreating what I had as a kid, and we all like performance, but I really like reliability and durability most.

So what I am hearing is that the packages claiming to be "the correct" top end replacement, it's not really all that correct-looking. I would think the steel inserted aluminum would be "better" than original because of the better cooling.

I don't hear you saying "anyone would be a fool using old Honda parts with all the new options out there". One ad says you should use old cylinders for pencil holders... Seems these bikes kept running and were considered overbuilt in their day. THAT is what I'm trying to recreate.

I really do appreciate your response.

Clark

YOU MIGHT WANT TO CH ECK OUT THIS
WEB SITE---- www.powroll.com
THEY LOOK LIKE THEY HAVE A FULL LINE
OF ENGINE =REBUILDS --YOU SHOULD
TAKE A LOOK AT IT..
GOOD LUCK

The combination of a weak dollar, every vendor claiming to have the "best" parts, along with lots of options can make for a very long discussion.

Bone-stock will be the most reliable/durable. It will also be the least powerful. The cost of a bore-up kit is close to overboring an original cylinder. An aluminum cylinder will radiate heat more efficiently than solid cast iron; it'll also look & sound different, aluminum cylinders "ring". Whether added displacement and torque trump completely stock appearance is your call. Rebuilding a stock Honda head is usually less expensive than any decent aftermarket replacement and I've seen some real junk head assemblies. However, power is made in the head and there are some quality aftermarket big valve/big port setups out there. They won't be the cheapest.

Like most of us, you are probably going to find out that matching reality to expectation based on decades-old memories presents a moving target. Hindsight, in most instances, is brutally 20/20. In this case, probably not. "That was then, this is now" can knock off those rose-colored glasses of memory in no time, especially if you plan on doing any street riding beyond 35mph. One nice aspect of these bikes is that, like any other hobby, they tend to remain works-in-progress. Changes/upgrades can be made in stages to suit your tastes. It's not like there's huge dollar amounts involved. Nearly any performance mods are bolt-ons and as such, reversible.


Going strictly by what you've said:

I am basically recreating what I had as a kid, and we all like performance, but I really like reliability and durability most.

I'd suggest doing a stock rebuild or stock rebuild with a bore-up kit only. The extra displacement, by itself, will give you a nice boost in torque and maybe an extra 5mph on the top end. I doubt that durability will be affected. Rider perspective changes quickly. What feels blindingly fast on the first ride may seem sluggish after a few miles. Should this turn out to be an evolutionary process, as it has been for most of us, you can always make the bike faster at a later date.

RacerX, I appreciate your suggestions (and your writing style!). I don't really like the pinging sound in aluminum cylinders. And I like relative quiet. When these little bikes are running well, they don't disturb the neighbors, much. Thank you for the thoughts. If I could have anything, based on this conversation, it would be a steel cylinder 88cc with an improved stock head, but I will settle for bone stock.

When I was a kid I probably weighed 135 and I don't remember having top speed problems (49 mph flat out, but 40s around town were reasonably easy). I'm 180 now, so my mileage will vary....

Chris, thank you for turning me on to Powroll! They have nice pistons, but no cylinders, only cylinder honing at $130. This is at first glance, I'll keep looking.

Best to you both,

Clark