Dax gp50 9hp wow !!

^^^^^P.M thatsdax he has'em
My mate went over the hangers at 30mph and broke his back due to his flimsy single walled rim collapsing when riding a ht that wasn't even really that quick.

am I being a pita if I say my bike owes me about 30bux completed.
In saying that though I paid for it with 15hrs labour of building motorized bikes then made up some brackets and what not. Luckily enough it came with a ktm fat boy pipe and the carby + I reused my HD rim off another build I just sold.
I just used the HT throttle cable but I had to remove the metal elbow that sits on top of the carby and just feed it straight into the top of the carby (its still seated) and tapped the crap out of it then took the slack out of the cable at the throttle grip tensioner. It working fine..

Good luck with your build M'D be sure to take progress pics and postem up somewhere.
Touche with your comments.
 
Last edited:
my rear rim is double walled with 12g spokes. this rim is as close to a worksman as you get without the pricetag. i just ordered it off ebay cause i needed a rim. it turned out to be a custom rim. most cruiser rims come two ways. standard spokes with a standard size hub, or 12g spokes with a slightly larger diameter hub. this rim is steel, double walled, and has 12g spokes, but with the standard hub size. and i paid 45 bucks for it. unfortunately the seller has closed their store on ebay, but i might see if their website is still up. southern cali customs is the company.
 
Thank You for the heads up on the engine breno - im sorry that your friend broke his back...

i never had any problems with my bikes, but i always put the best parts on that i can find, steel chrome plated rims, shimano Deora Hubs, heavy duty spokes, etc...

how is the HD rim holding up???
 
I know that dax was saying a 415 chain wont work with this motor...

however, i just test fit my #41 chain, and it seems to fit fine, no binding (yet)...

You should still get a 420 chain, since this is a 9hp motor...but im gonna experiment and try to run it with what a i got
 
HD rim is holding up sweet. Though I need to take it off again back off all the retainers and re-locktite them all and re-true. Its lasted all in all about a year without a buckle untill just lately but in saying that some of my spokes have been loose for a while and I've been slack.
I have the HD #420 chain and run it fairly loose with the a standard chain idler. Really gotta sort out a new chain idler lol.. that thing is going to hurt me bad one day..touch wood.

Hey M'D what size rear sprockt are you going to go with and if you dont mind me asking how much do you weigh?
 
i got my rims from bike buyers dot com and bought the deora mountain bike hubs from a local store here in the city... they have been great wheels thus far...

i believe they would definitely hold up to gp50...

i would like to convert the sprocket mount to something a little more beefy - how do folks here feel about using the sportsman's sprocket adapter with this engine?
 
I have had no problems with my stock rear schwinn 7 SPd rear.. Rag joint with a 50 tooth sprocket. But I'm looking to get a sealed bearing rear with disc mount adaptor. You can feel the rear shift a bit from the torque on the power side. This engine has lots of torque but its applied a bit smoother at first from the cyntrifical clutch. It slips almost halfway in the rpm then locks solid. You have to be on the gas just to cruz to engage the clutch. Not a smooth slow speed bike but will launch like a drag racer.

PS DONT Use the cranbrook rear or the bike for this gp50 clone engine. Much thinner wall then schwinn or others. I've built manny cranbrooks and have allayed had problems with the bearings in them. They don't last and need lots of attention. A commuter I built lasted 1300 miles and had 5 bearing swaps and had to dremmel the race out caste its soft metal and got messed up. Plus a coaster break is a bad idea on this engine. It's like an automatic car. You are fighting the engine while breaking
 
I use a gutted coaster to be able to use the Sportsman adapter. One advantage is it has three bearings, two on the drive sprocket side where most of the load is. The Lifan 125cc 4spd loads the sprocket heavily in both directions on upshifts, downshifts. and heavy engine braking. No problems with the adapter. Should be a piece of cake with the GP50. I am running a higher quality wheel with .105 spokes and double wall rim. Wouldnt try it on a cheaper one.
 
Finally got my motor mounted and test run...

wow, this thing is no joke...it sounds beastly...INSTANT throttle response...i cannot wait to ride this thing.
 
Last edited by a moderator:
motor_bike_fanatic said:
all synthetic air cooled 2 cycle oil is universal. Thats why all it says on the bottle is synthetic oil for use in ALL 2 cycle air cooled engines. says that on every bottle of oil I ever bought. says it on Pennzoil, says it on Lucas, says it on the no name brand I buy at walmart. thats how I figured out I could use walmart oil. I was using Lucas, but saw the walmart stuff at half the price and found out it was the same. Had this engine for a year and only used Lucas for the break-in. Im gonna clean my spark plug next weekend so I can do a proper color test, but so far I see no signs of this oil hurting my engine. But, if this engine goes up to 10,000, it probably needs racing oil. In all honesty, you turned me away from using this engine already. $500 for the engine alone, then I need a frame, a different throttle cable, a different sprocket, a different pipe, special oil. Probably talking up to $1,000 total on the build at least, plus the time involved in building a bike from scratch and dialing everything in, probably at least a week. I may as well just buy an old dual purpose dirtbike. Thanks.
Click to expand...




i may be beatin a dead horse but not all oil is the same!!!!!!! i use lucas and i know that wallmart oil is not the same as lucas!!!! hands down.... and sorry not tryin to get in to an argument... just helping you realize it..





the link to my build... http://motorbicycling.com/showthread.php?t=37663
 
Last edited:
I ordered a factory pipe for the GP50. Once it gets here I will know pricing and quality. Looks good in the pics.. But I will wait and see how it measures up to the KTM factory pipe quality since I still have my KTM 440EXC. Pipe should be here in the next week or so.. Also have some 9T engine sprockets coming as this will aid greatly in getting correct reduction ratio. We do not want to eat up our clutches. Enjoy the ride.
 
Hay Dax. Have you counted the sprocket on the gp50?? Mine came with a 9 tooth. Ive been thinking of going with a 10 for more speed.. Why order the 9 tooth if they come with them already??

I'm running a 9-50 combo. And the clutch slips til about 20 or so. If I went with a 9 55 or so I'll have no top end speed. I really want to go like 9-45 or 9-47 but it will not have any off the line go.. That's y I want to experiment with 10 tooth...
 
Last edited:
Yea i would change both not just go 10 tooth...!

Has any one really tested /dyno these to check on that 9 hp rating. I would like to see what these really have.I'm suspicious of that 9hp myself... I have 2 of these and they run a bit different from each other. I even swapped carbs to c if it was a bad carb but ran the same. So I think their isnt as strict quality standards for these like the morini. Bummer
 
Last edited:
OOooOo 9t! how much? where? My gp50 has 10t. And sportsman wants $60 for 56t rear dinner plate...gotta be a better way
 
Last edited:
i think you can get a fancy one from kings in any tooth count you want for much less.. i ordered my 50 tooth from dax and it was reasonable.. he may carry a 50+ tooth....
 
Ted said:
Here's a site that may help you figure what your going to get with a sprocket change. You may want to change the rear sprocket rather than the front one to get a better ratio. If your clutch is slipping up to 20 now adding another tooth will make it slip a lot more and a lot longer. You might want to look at lighter springs also, you have 9hp, use it.

http://www.compgoparts.com/TechnicalResources/SprocketCalculator.asp
Click to expand...


Lighter springs takes away the power. I have been messing with these motors for mebbe three years now? IME. with these motors it will no longer be a 9x power motor. These motors do not generate 9 horse power right off idle. The sooner you can get into the power band ''revs'' then you shall feel the excitement and experience of a 9 hp motor.

Its like a chain saw if you put a chainsaw into a partially cut tree with out revving it first it will likely '''never ever''' get to full rev's


A clutch matched to this process is for me where the glory is.. Here is a link and a quote: http://www.motomx.com/clutch_information.html

How the bike is presently geared. You have to treat gearing and clutch set up independently. Example: If you were to make a rear sprocket change to increase top end speed, (Less teeth on rear sprocket) then you loose some bottom end power. Now with the clutch set up you can change your power curve to compensate.

'''''ignore their washer stacks all together we use a totally different configuration in our clutches''''''

I just like the way that quote is worded!

Principals of physics still apply. The only thing I have ever got and used out of this link that has applied to me is the oil I use and my stall. I am sitting at over 5k miles on one clutch here and never did change out my washers for new ones. Been consistently changing my oil every 9 hours or so of ride time.

Our clutch and bell diameters look to be the same. Yet their washer stacks are totally alien to the stock config that came with any of my clutches. I do not recommend trying them.. My own experience at one time was disappointing. To drop stall just simply removed the flat washers systematically until the desired result is achieved.

I imagine that in major heat races it could be advantageous to change oil on occasion? As the oil's viscosity would perhaps stay more consistent in the clutches over all tuning?



Found in my experience the type oil used effects clutch performance for me substantially. Saw changes in personality from winter verses summer. I set it for a high stall then use thicker weight oil to make it engage sooner off idle. Changed and finessed the whole feel of things for me.. These clutches need a little break in time too. I use the same brand oil in the link ... 90w tho. lately this year in the summer with 10% lucas heavy duty oil stabilizer.

Good luck guy's Cheerio!dnut
 
Last edited:
thatsdax said:
Clutch is kicking in at around 4000rpm. How about yours? Any pictures? How is yours running? What size rear sprocket are you using? Any pictures?

Have not had to adjust auto clutch yet since my install is not even finished yet. Break in is 5 hours. Avoid full throttle operation for 5 hours the book says..
Click to expand...
I'm running a 52 tooth rear sprocket on a 26" tire with my morini S6-C (converted to S6-S). 50 ish is what I get uphill. Great acceleration. I ordered a disk brake rear hub and installed a Top Hat adapter onto it. Allowing the rear sprocket to attach to the rear rim. Definitely the way to go for a mountain bike rim application. The rear sprocket was a bit big to allow the chain to clear the frame. So a chain tensioner had to be fabbed and welded to the bike. Worked out fine.
 
You must log in or register to reply here.
Back
Top