From whom to get a 4 stroke?

The Grubee Kit offered by bicycle-engines.com seems to be the best of what is currently available. It can be purchased with a motor, the HS clone of a Honda for around $400.00 +- or as an installation kit without motor for around $220.00+- and then you can get a Real Honda GXH50 from Small Engine Wharehouse for $210.00. Two other vendors are currently in the prototype/testing stage of building alternative reduction gearboxes/cvt? but are not currently available. Also the folks at Sick Bike Parts are working on building a version of their shifter kit to work with either the Honda motor or its clones.

The major difference between these 4-stroke kits and the HT 2-stroke is the need of the additional reduction gearbox. The HT 2-strokes have a built in reduction of 4.2:1 For the 4-stroke kits this primary reduction is provided buy a 3.7:1 reduction gearbox that is bolted onto the output side of the motor. This reduction gearbox seems to be the weak link in the 4-stroke kits. The current version of the Grubee gearbox (The Stage III) is supposed to be an improvement but has only just recently become available (Oct. 08) here in the US so its to early to tell how how much better it actually is. The early reports from the two new alternative prototypes from Quenten Gunther and Mike at Simpson MotorBikes have been good but I still have not seen any projected availability dates or pricing on either of them.

The Second major difference is the need for dramatically wider crankset for the 4-stroke kit. The currently available solution to this problem is a really bad one. It requires the use of a 9in. long BB spindle that uses a seperate cottered crank-sprocket and two seperate crank arms. This crankset also requires an adapter to mount it into the larger BMX/Cruiser BB shell which is an additional $30.00 - $40.00 depending upon which vendor you purchase the adapter from. Its a very ugly set up to say the least. There are whole threads on this crankset here and at the other forum.

The Third difference is the 4-stroke kits use centrifugal clutches and Pull starters rather than the manual clutch and pedal starting of the 2-stroke kits.

ocscully

i like the dax titan. i had one and just got another one i am building now.

Centrifugal clutches? No thanks, i'll keep my 2-stroke till they get a real clutch and decent reduction on there.

just finished building a 4 stroke from bikeengines.com, not a bad kit just poor in overall quality, the service from them was excellent however. make sure you have a three piece crank setup on the bike your using or its another 50 for the crank adaptor(then add on pedals too!) The gear box is not noisy at all, however i have to figure out how to adjust the clutch so it dosent bang hard into gear. I also have a big hesitation in the throttle response that does not go away with carb adjustments. Hough, if you have any ideas id greatly appriciate it. Other than those two things it runs well and I'm sure once i get the bugs out I'll be happy with it. I have three other Dax two strokes and am spoiled with them, right out of the box they all ran well and continue to do so. If i had to do it over i would get the Honda.

ebmvegan said:

ocscully, Thank's for the info.

I've heard that the gear box can get very loud. Is there a sollution?

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The original Grubee gearbox was reported to be very loud, and there was what could be called a recall on these gearboxs. The replacements were said to be an improvement. The latest Type III is supposed to be even better although it appears to be the same except for better sealing and increased # of bolts holding the two halfs together. Alternatives: ? Sure there are alternatives but they would all add quite a bit of expense. You could use a Staton-Inc inside drive gearbox, but it is larger and goes for $350.00+- including a clutch and the adapter necessary to fit the gearbox to the Honda motor, but the quality is far superior to anything offered by Grubee. You could also look into the Comet CVT variable pully system but I believe they are limited in how much reduction they offer. Then there is the total custom drive train using a jackshaft using chain or belts?

ocscully