1st build revisited

GoldenMotor.com

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
I rebuilt my first motor assisted bicycle last week with some different parts and last year's DAX motor with 3 out of 4 head studs helicoiled. Here's the scoop:

Schwinn Hi Timber(same old bike) 21spd mtb:
26" 1.95 front and rear kenda semislicks thornproof in front and slime rear, one of my slimes broke
36T sprocket from (boygofast) i donno if they're still around
w/ #41 chain from (tractor supply)
(skipu) spring tensioner with 10t idler gear ebay
(Thatsdax) 66 cc motor no porting or modifying of ports in any way
(arrowmotorizedcycles) reed block
crmachine stage 2 head(via arrowmotorized cycles but from crmachine)
NGK bp8hs plug
RT carb(thatsdax) with 60 jet(sickbikeparts)
(arrowmotorizedcycles) torquer2 exhaust
87 octane gas with 10% ethanol (yuck, i was in a pinch, ethanol runs funny and smells bad)
ipone strawberry scented scoot city synthetic oil 36:1(scooterworks)


right now ive topped out at about 30 mph and i can pull 33 but it runs very rough at that speed. Im looking at other posts and thinking about using some more aggressive parts, but right now this is my business model as im trying ot build more bikes for more people around me.

I really like the RT carb now that ive got one that doesnt leak, my first one i messed up it the float and or the bowl gasket andit leaked all my good Hi octane ethanol free gas down the drain in a few days

I really like the skipu tensioner but mine is getting worn and i need to rebuild it, it is starting to lean in.

I also really like the crmachine head it keeps me worry free about overheating the head too bad.

Im thinking about doing a few things but im not sure what to try first:
1: switch to 93 octane ethanol free. I know these engines arent meant to run with ethanol and im concerned that i am not getting the full potential with cheap gas also this is the easiest change i can make
2: move up to a dellorto 19mm pbhg carb(sp?) I have one i ordered but i dont have any idea where to start with tuning, i just bought one because i saw crmachine running one in a video on his website
3: I have a arrow boost ported cylinder body that came with my reed block, i was avoiding using it at first because i wanted a baseline from which to see where my RT carb was running well. I know the exhaust port is considerably wider and i was planning on moving right back to a 70's jet and then jetting down.
I dont know ill probably follow up on this post what i did in what order but i really want to try to have a systematic approach so i can see the power increase. I miss going 40mph every day. Now that ive ditched the nt carb i think ill be able to ride 40 without being afraid of starving the engine. I might even switch to a 32T sprocket i have laying around, the RT carb has no problems taking off from idle.
 

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
Today, still couldnt top 34mph downhill. Replaced e10 87octane gas with 87 octane ethanol free 36:1. no improvement...
Going to use boost ported cylinder tommorrow and try to squeeze out some more power, moving back to 70 jet in rt carb
 

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
Rebuilt my engine with ported cylinder body from arrow motorized cycles, this is a pk80. Should have known, my clearance was really close. Changed the jet to 68. I tried cranking it up and heard a bad tapping when it fired up. Took the engine apart again and used thicker head gasket goign to fire it up again this week. Also switched from bp8hs to b8hs plug.
 

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
put in 65 jet in my rt carb
also running a thicker head gasket.
I went to go find thicker base gasket material but i couldnt find any, and i am running a b8hs instead of a bp8hs plug. I just reached 34mph on flats and 39.8 going down hill before i ran out of road.
 

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
running a bp7hix plug today, and a 66 jet in rt carb. Going to try to hit above 40 before i consider putting on smaller sprocket. Also bent my exhaust tip to clear my seat a little more. Will post results later. Also i ordered a trike conversion kit and my Dax balanced crank engine came in
 

BonusParts

Member
Nov 28, 2012
168
0
16
SE-PA
running a bp7hix plug today, and a 66 jet in rt carb. Going to try to hit above 40 before i consider putting on smaller sprocket. Also bent my exhaust tip to clear my seat a little more. Will post results later. Also i ordered a trike conversion kit and my Dax balanced crank engine came in
On a 36t you should be able to hit 42-44mph on a decent motor with some small mods. i did 43.62 on my gt5 grubee motor, just porting, compression and gaskets as far as mods. GPS verified. also on a 36t - thats revving to about 8300rpm
 

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
im running out of power at about 34 mph and im having to unweight my back wheel and get really aero to get going up to 39 mph. I feel like i dont have something set right.
I wish someone sold a bigger exhaust pipe that i knew would work with my motor i also think i need to try my 19mm dellorto phgb carb out
 

16v4nrbrgr

Active Member
Mar 17, 2012
1,728
4
38
North Bay
Could you set it up geared lower and try to get more revs out of it with a different ignition and that big carb? 39 MPH is quite thrilling with the HT, I bet it sounds like a dirtbike at full chat!
 

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
finally took apart phbg carb. fred has me convinced in ordering a new pipe and i found out that i have a 50 idle jet in my phbg carb which is why i couldnt tune it properly. I just need to get more power out of my setup. So im going to try these upgrades in order:
phbg carb 35 idle jet, 74-78 main jet
then
snake racing pipe
then
upgrade off of stock cdi to huffy davidson cdi
 

graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
my new set up will be:
Schwinn Hi Timber(same old bike) 21spd mtb:
26" 2.4 cst cyclops front
24" 1.75 slick or 24" 2.4 cst cyclops rear
34T sprocket from kings sprockets
w/ #41 chain from (tractor supply)
(skipu) spring tensioner with 10t idler gear ebay
(Thatsdax) 69 cc motor stock bottom end
(arrowmotorizedcycles) reed block and ported cylinder
crmachine stage 2 head 6.0cc(via arrowmotorized cycles but from crmachine)
NGK 7 series irridium plug
RT carb(thatsdax) with 66 jet(sickbikeparts) or
dellorto phbg 19.5 AS with 35 idle jet and 78 main jet
needle in bottom position to start
(arrowmotorizedcycles) snake pipe
93 octane gas with 10% ethanol (yuck, i was in a pinch, ethanol runs funny and smells bad)
ipone strawberry scented scoot city synthetic oil 32:1(scooterworks)
stock CDI


especially excited about the pipe. Hoping to kiss 48mph