I have several antique motors built by Tanaka, but mine are all front fork mount, friction drive... a different animal to be sure. The Tanaka motors were well made, but ones like I had are no longer being manufactured. Tanaka (google it for the American distributor) has some replacement parts, but others are not available which makes keeping them running a hassle. Also the friction front mount were only 26cc, hardly enough to make much of a difference other than flat land travel. The one in your photo looks more substantial and no doubt has higher output. My question to you is: is your interest as a collector or do you intend to use it regularly? If you are a collector and it is rare then it iw worth whatever someone is willing to pay for it. But if you're going to use it regularly I'd make sure replacement parts are available and technical information is also out there for reference. Just guessing, but I imagine these are few and far between and that parts are even more scarce. If that assumption is true then a HT motor makes more sense. For one thing you have this forum as a resource. For another you can buy a motor which is new for a good bit less than $200.00. Third, parts are readily available and inexpensive. I'd go with the HT motor or if I wanted to pay more and get more then either the Italian Morini (sp?) or a 4 stroke kit. I hope this helps you think it through. If you go with the Taz I hope you'll keep us informed on how things are going.
Silverbear

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Someday when I grow up I will probably lose interest in toys with wheels, but until then...