acheiving race bike status

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graydog8josh

Member
Nov 23, 2012
450
4
18
Starkville,MS
I am on the quest of true high performance. Ive started budgeting my meals, reading two stroke tuning theory and trying to get my hands on every broken motor i can to brush up on my troubleshooting skills and make money. All my money is going into making my bike a real contender and not a pretender.

However, right now I'm working with this:

Steel hardtail 26" mtb frame wiht cloud 9 seat (diamondback)
36t sprocket with #41 chain from tractor supply and arrow motorized cycles case saver

dax balanced gen iv engine
modified piston from crmachine
stage 2 cylinder body from cr machine
power plenum from cr machine
sha 16.16 carb
ethanol free gas(really hard for me to come by here in town) with mmt octane booster and ipone strawbery synthetic scooter 2 stroke oil
ngk bp8hs plug
hd lightining cdi
SNAKE PIPE!!! from arrow motorized cycles

its a little sluggish from 0 to 15 but rockets up to 40+ mph from 15.
I think i have a rich tune, but predictably its hard to tell with mmt in my gas the plug is a funny rust color.

I just ordered a 21mm phbg carb and a new face for the power plenum that fits the 21 mm carb better, and im hoping thats the missing piece of the puzzle. Its either going to be the phbg carb or the mikuni 18 that unlocks the ultimate power of my engine. Only thing left i think that i havent done is a balanced race crank.

I know there are racers out there that would say to have a race bike you have to race, and thats what im working on next. I would like to get out to the races so i could ride hard and fast, and meet great builders and riders alike. Right now i just don't know how i would get out there.
 
KCvale

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
Just one tip...
NGK 5944 (BPR7HIX) Iridium spark plug.
I haven't used a stock plug in any 2-stroke build for over 2 years because for under $10 these baby's really do the job in these 66cc 2-sroke engines, enough to feel.
 
KCvale

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
bairdco said:
a number 8 plug may be too cold. i ran one at the last race out here in 90° weather, and switched to a 7. bike ran a lot better...
Click to expand...
Ya, the heat range number in the middle can make a big difference in how much heat the plug will dissipate to the head.

Too much heat dissipation and your engine never gets to ideal operating temp, typically in really cold places.

Not enough heat dissipation and your engine overheats.

This is a good read for finding your ideal heat range.
http://ngksparkplugs.com/tech_support/spark_plugs/p2.asp?mode=nml



The more white you have in contact where the threads are, the more heat is transferred to the cooling fins, and the pink is just providing an air gap to keep heat in.

I would also stipulate that an air cooled motor dissipates much more heat much quicker in a freezing wind opposed to frigg'n hot stale air.

----
Engine Speed and Load

* If the engine is to be operated at high RPM, under a heavy load, or at high temperatures for long periods a colder heat range may be needed.
* Conversely, if the engine is to be operated at low speeds or at low temperatures for long periods, a hotter heat range might be needed to prevent fouling.
---

I live in the desert, 7's work well here but I like to keep a couple 6 and 8's around for certain conditions.
 
T

Theon

New Member
Jan 20, 2014
1,440
6
0
FNQ Australia
Your 16mm carb is likely big enough to get you a little more from your motor, and may not be what's holding you back? 50Mph should be possible from that carb, Its about sacrificing a fair bit of low down, and getting enough power still at 9000+ revs to keep accelerating though.
So getting your exhaust to work in sync with your port timing from +7000RPM. It would be interesting to get your port timings, you may just need to lift the jug a little or give it a bit more exhaust duration with sacrifice to low end to get more top speed?
 
massdrive

massdrive

New Member
Oct 3, 2013
454
3
0
Las Vegas
graydog8josh said:
I am on the quest of true high performance. Ive started budgeting my meals, reading two stroke tuning theory and trying to get my hands on every broken motor i can to brush up on my troubleshooting skills and make money. All my money is going into making my bike a real contender and not a pretender.

However, right now I'm working with this:

Steel hardtail 26" mtb frame wiht cloud 9 seat (diamondback)
36t sprocket with #41 chain from tractor supply and arrow motorized cycles case saver

dax balanced gen iv engine
modified piston from crmachine
stage 2 cylinder body from cr machine
power plenum from cr machine
sha 16.16 carb
ethanol free gas(really hard for me to come by here in town) with mmt octane booster and ipone strawbery synthetic scooter 2 stroke oil
ngk bp8hs plug
hd lightining cdi
SNAKE PIPE!!! from arrow motorized cycles

its a little sluggish from 0 to 15 but rockets up to 40+ mph from 15.
I think i have a rich tune, but predictably its hard to tell with mmt in my gas the plug is a funny rust color.

I just ordered a 21mm phbg carb and a new face for the power plenum that fits the 21 mm carb better, and im hoping thats the missing piece of the puzzle. Its either going to be the phbg carb or the mikuni 18 that unlocks the ultimate power of my engine. Only thing left i think that i havent done is a balanced race crank.

I know there are racers out there that would say to have a race bike you have to race, and thats what im working on next. I would like to get out to the races so i could ride hard and fast, and meet great builders and riders alike. Right now i just don't know how i would get out there.
Click to expand...
I have my engine set up pretty much as yours (but with VM18 and plenum intake)
http://motorbicycling.com/showthread.php?t=52165
I can tell you the VM18 is not the answer to you quest for speed. Just like your engine mine doesn't start to come to life until about 15mph. My friend Risingsonn runs a almost stock Dax engine with a NT carb and although I have a little better low end torque and acceleration he tops out at well over 40mph. I'm still trying to break through. Good luck.
 
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