HI All, two not so simple questions.

Dax engines are some of the best, if not THE best engines you can buy.

And are you referring to a shift kit?

I agree on the Dax engines, I've bought 4 of his bottom ends and they all tuned out really good engines. I put mine thru a lot and they're just rock solid dependable.
Since I'm always trying to get the most performance out of the engines I build I use the best parts I can find to put them together, the Dax bottom ends have proven themselves bullet proof at 5+ hp and 10,000+ rpm.

For the GRU you speak of, a jack shaft is probably your best bet, it can be as simple as a shaft with 2 pillow block bearings and a set of spockets, the input sprocket needs to be bigger than the output, but both sprockets can be set up on the same side of the shaft, so let's say you need twice the torque to the rear wheel, you would want a 20 tooth input and a 10 tooth output to the rear wheel, your top speed would be cut in half, but your torque to the wheel would be doubled... great for pulling or hill climbing.
You could use a 15 tooth input if that cut the speed down too much and still come out with excellent pulling power.
This would be a viable alternative to running a huge rear sprocket.

I 3rd that with the dax engines.... best most dependable and fastest with simple mods that I have had.

DAX Bottoms are best. in my opinion... I'm running 3 of'em now. All smooth as butter.
http://motorbicycling.com/album.php?albumid=1811&pictureid=10632

While I have not run the Dax motor, I do have a GenV which is the same engine.
It's identical in every way to the $160 Cheez Fickenworth kits I have been buying lately.
The first two kits I bought simply to swap out the motors with stuff from my stash so I could keep the excellent kit motors for myself!
These engines have HUGE transfers and excellent castings and the bottom end has the better balanced 40mm stroker crank exactly like the Dax.
All the usual kit parts but adds the RT carb (WITHOUT the silly second fuel valve!) and a four bolt chain tensioner with the angled slot (slightly better)
It's a screaming deal for $160 shipped and beats the Dax all to chunks.
Contact him on Facebook Motorbicycling.com (PM "Cheez Fickenworth") group and order through PayPal for security!
I am at three kits and counting and have been VERY pleased! I'll be buying a fourth as soon as my current bike sells.
Food for thought.

Those engines do look good and the price is definitely good...
So far my best engines are using Dax bottom ends, mzmiami cylinders, fred head, modified dirt bike pipes, and the mikuni vm18 carb connected with the adapter sold by mzmiami.
The cylinders he sells have huge transfers, nice wide exhaust ports, and the intake ports are good sized too. The ones with the 40mm stud spacing have slightly smaller round intake ports which is good for doing your own port work, but the 32mm stud spacing cylinders do have some healthy intake ports so whichever spacing someone chooses, they both will perform just bolt on and go, but they'll save someone a lot of porting time since the ports are already so big.
I've bought 3 of the 40mm stud cylinders and 2 of the 32mm ones and they all look really nice with nice thick fins on the outside and huge ports on the inside...

http://www.ebay.com/itm/MOTORIZED-BICYCLE-PORTED-40mm-CYLINDER-SET-FOR-66-80cc-MOTOR-/281784575281

are these the cylinders you're referring to dave?

tgaydos said:

http://www.ebay.com/itm/MOTORIZED-BICYCLE-PORTED-40mm-CYLINDER-SET-FOR-66-80cc-MOTOR-/281784575281

are these the cylinders you're referring to dave?

Click to expand...

No... no need to buy the ported ones unless you don't want to do the porting yourself... I buy the un ported ones then do all the port work myself. I'm sure the ported ones he sells are good but I'm really picky about port timing, duration, and the physical width of the ports. If you look at the intake port on his 40mm bolt spacing cylinders you'll see that they are round and smaller than the ports on the 32mm bolt spacing cylinders... this is great for those who want to do their own thing with the porting and good for those who just want to bolt on and go, the intake port starts out at 19mm and tapers down to about 16mm at the cylinder with a long straight shot into the engine which makes for a lot of torque in stock trim but still capable of a lot of rpm up top, that taper accelerates the air going in so it can pull in more air than there's room for at higher rpm's which makes for higher transfer pressures and even more that can get stuffed into the cylinder when in its powerband, which equals more power to keep things simple. With a custom matched intake and an 18mm carb this would make excellent power as well as really nice torque down low. The transfers have the flat tops and they are nice and wide as well as being aimed nicely so all that needs to be done here is the typical casting ridge cleanup.
The exhaust ports are also about 25mm wide on these so they're pretty much ready to go right out of the box, but you could open the exhaust up to the 29mm limit, then all that's needed is to raise the roof if more rpm is desired. Otherwise the 40mm bolt spacing cylinders are pretty much bolt on and go performance, with just enough room for the finishing touches to get the port timing where one wants it to be.
The 32mm ones are very similar except that the intake port is typical where it's short but wide... also really good for top end power but with enough room for end user improvement if desired.

The ported cylinder in your link is nice but you would need to find out from him where it's timed for so you can know how thick the base gasket needs to be for best performance, but it looks like it's set up for at least an 18mm carb and a good pipe which should provide excellent performance for someone who prefers not to port their own cylinders... some of the bikes his customers have are Really fast so I'm pretty sure his pre ported cylinders should be good too.

These are the ones I buy... http://www.ebay.com/itm/MOTORIZED-BICYCLE-66-cc-80cc-32-MM-CYLINDER-Good-Quality-/271894008452
And these... http://www.ebay.com/itm/MOTORIZED-BICYCLE-66-cc-80cc-40-MM-CYLINDER-Good-Quality-/271952264441

There's also quite a price difference if you can do the porting yourself....

good information as always dave thank you for the input, i was more or less making sure i got the right seller on ebay.

For the cylinders... definitely the right seller... these are the best quality cylinders I've seen so far, not only with the ports but just the total build quality. Fins are cast nice and thick, plating inside looks great with very minimal overhang in the ports, and of course, huge ports on all of them.
When I see stuff like this I usually buy as many as I plan on using then pass the word on in the forum so I bought 6 of them last month that either have been or will be installed on Dax bottom ends.
So far I haven't seen enough significant difference in pistons to say one vendor has some really good ones compared to the others. One thing I would really like to see is a set of rings that could be gapped by the end user as these rings have huge gaps that are too wide from the factory. If these gaps were tighter they could be set by the end user with a jeweler's file for better compression due to less blow by.

got wrong pistons shipped from there & sent back a pic of the boxes, so they shipped right ones and paid return shipping

got one cylinder once that had been dropped or something and had a ding in bottom that wouldn't allow piton to go thru - was fairly easy to fix tho & ran good then

That's good to hear... I've just started buying from him more on a regular basis and haven't had any issues at all with anything he's sold me in the past but it's good to know he's another vendor who will take care of problems quickly. I know a few months back he didn't have the 40mm spaced cylinders up for sale so I asked him if he was still planning on selling them, he replied quickly and told me about when they would be back in stock as well as other goodies in the works... I got the cylinders I needed once he had them in stock, but it's those other goodies in the works that keeps me checking his items for sale regularly... One of them is his new pipe which is basically a nice treatland pipe built for the CG engines, I hadn't bought one yet, but others have and should be reporting back about how they do... He told me about other stuff too so I check his site regularly.

yeah, lots of sellers got hung up on that port strike

I've got a Dax F80. 975 miles so far and still runs like new.

Dax google are some of the best, if not THE best google you can buy.

That's why I recommend them so much... my own personal experience with them as well as numerous positive reviews make me very confident in recommending his engines and bottom ends when people ask which engines or kits are the best.

Davezilla said:

That's why I recommend them so much... my own personal experience with them as well as numerous positive reviews make me very confident in recommending his engines and bottom ends when people ask which engines or kits are the best.

Click to expand...

Amen......... Im a believer in the dax 40mm stroke engines, haven't tried one of the two GT5 type engines I got from dax last year yet so not sure what I think of them yet, but I really like the PK80 40mm stroke engines Ive got from Duane.