stroker crank

[Johnny 5]

I found the noise from my wife's blue dune 150. I split the case and removed the crank after removing the gear behind the variator. I had to use a jaw puller with a bolt through the puller arms to get that stubborn gear off. Other than that it came apart easy. I have yet to buy the starter clutch socket for assembly, I used a flat punch and a hammer to remove the reverse thread nut. I can hear the scraping noise/rattle that at idle would cycle every 2 seconds and get faster with rpm. Our last trip to the desert in april 2012 I had just installed a 58.5 srp high compression piston kit. The compression was 125psi stock and after the kit install the compression was 145psi. After messing with jetting I found that 125jet was too rich no power,122 felt better but plug still very dark, 120 power was good and plug came out tan at wot run. The buggy ran awesome until the last day of our trip and I was running the buggy full throttle for a long time. I think the 20psi increase of compression on the 3 year old motor and me riding it like I stole it did it in. Now to my question is a 2mm stroker crank worth the extra money and the timing chain problem I have run into. I bought a 1.6mm spacer and with 2 base gaskets, the base gaskets are .5mm thick so 2.6 mm space total. Now the chain is not long enough, I bought a 92 link chain and you would need to space it 6mm to work. I have not bought a crank yet. I did buy the ncy bore up tool and planning a 62mm piston kit for sure. I have heard of cutting the piston down and notching the valve reliefs, but that makes the piston thin and can get hot spots. Now if I use the 1.6mm spacer and one .5mm gasket and honda bond the spacer to the block the chain is okay. But now the problem is the head is .5mm closer and the compression will be to high. I am about to just put a stock crank in and port the head a little more and add a a 12 cam. So 62mmx62mmx57.8mmx0.7854=174.5 cc. Any body got any good results with stroker cranks. I also worry about piston side loading at high rpm with stroker cranks. We ride alot of wide open throttle in the desert and am not sure if a stroker crank is good for this type of riding. I am making myself a little nuts playing all the possible combos. I cant leave it stock because I have got gy6 buggy fever. Any suggestions?

[Johnny 5]

I just read my post and forgot to say the rod bearing was grinding about 1/4 of the rotation causing the scraping rattle noise at idle every 1.5 or 2 seconds. I am still not sure on if I want to do a 2mm stroker crank or a stock crank. Is the power worth the extra 100.00 bucks? Any body have any good or bad results? I have the money to buy a crank but not sure which one. Thanks again.

[ckau]

Originally Posted by Johnny 5

We ride alot of wide open throttle in the desert and am not sure if a stroker crank is good for this type of riding. I am making myself a little nuts playing all the possible combos. I cant leave it stock because I have got gy6 buggy fever. Any suggestions?

Yep! there's all sort of combinations. You have to ask yourself what is most important. power or dependability? There's that compromise thing, performance versus practical. As you go more exotic so dependibility goes down at a alarming rate!
IMO- I would keep displacment and stroke as small as feasible. Look for gains with head work as in porting, valves and springs. A suitable cam. a good exhaust header. a matched carb. These will give good power without sacrificing dependability.
Focus on keeping the motor cool. Heat is your worst enemy! Smaller displacments have thicker cylinder walls to aid in cooling. Oil coolers are a must! Jetting rich as possible helps too. Header wrap keeps heat in the pipe and blown out the back! All these subtile additions add up to give good power without a loss in service.
I truely love a full bore, stroked gy6! I love the way it sounds the way it feels, but the thrill is short lived! There's as much if not more tuning and rebuild time as there is riding time. Riding at home ? you know it's the way to go. but away for the weekend? I'd use a motor that won't leave me walking and spoil the trip.

[Johnny 5]

Thanks for the info I was going a bit crazy about the stroker cranks. I would like to try a stroker crank some day but for now I am going with the stock crank, due to the timing chain not being long enough to space the head a full 2mm plus the base gasket at .5mm.
I can do it if I use the 1.6mm spacer and one base gasket but the compression will be way to high and I am concerned about piston clearance at high rpm.
So I am waiting for the ups truck to deliver my stock crank and ncy 62mm piston kit.
When I ported the head/cleaned up the casting flaws took away the sharp edges back in 2010 December, I was amazed how smooth the power and it pulled at top rpm. This was a huge improvement that I could feel and hear. I am going to port the head a little more by cleaning around the valve guide and opening the floor of the port a bit more. I know not to make the port bigger than the intake manifold or the exhaust pipe diameter. The head was very restrictive compared to the howhitt head that came off the junked original motor. If I could I would use the howhitt head but the intake valve seat came out and bent the valve up. That motor stock had very good power and lasted 3 1/2 years.
I want to run a oil cooler but am concerned about it holding up in off roading conditions
getting bounced around.
Thanks for your help and when I get it together I will let you guys know how it runs.
I hope that going from a 155cc to a 175cc will be noticeable.
Here's our latest video-
http://www.youtube.com/watch?v=ekpsd...1&feature=plcp

[metalstudman1]

Beautiful area to drive!!! Great video

[chuckorlando]

I've had a stroked 180 built to the gills. Been running and running strong for many years. In fact, thats the only china engine that aint proved to be a POS.

I now run a stroked 400. I refuse to split a case and not up grade it. Nothing gives better low end grunt than a crank without giving up top end.

120psi sound way low to me. New 4 bangers are closer to 150 stock

[SYCARMS]

I have build several engines for customers as well as my own. I have as well as my customers had very good luck with stroked cranks.Sure the side loads will be greater but thats where a good quality cylinder comes in play. Most of the cheaper big bore kits use recycled cast iron sleeves which are softer then a higher priced high nickle content virgin cast iron. Most will hunt for the cheapest price on components which is a huge mistake when building a performance engine. Same with stroker cranks the cheaper ones are just stock components stroked. The good cranks will use a heavier rod and some use forged rods. The same principles apply as in building a 350 perf. engine. You will get out what you put in. CKAU is correct when he states reliability is sacrificed when building performance but to what extent depends on the quality of parts used. Chucks built 150 is several years old now and he does drive it like it's stolen. Mine and my sons were built in 2006, his has the 3mm stroke and mine 6mm stroke. No problems what so ever out of reliability and we drive the crap out of them. Most of your power will come from the top end but if porting your own head if not properly done can actually cost you performance. You just don't open them up, you have to know where to and how much to grind. Take two ported heads and put them on a flow bench, one will flow more then the other but the one which flows less will actually produce more power. It also depends on where you want your power. Hill climbing, circle track racing and drag racing all use different porting tecniques. When the top end flows the bigbore and strokers will really enhance the power since you are now capable to fill the cylinders. Stock parts are no different since you can purchase the cheap parts or quality parts which cost more. As far as the timming chain I have built motors with the 3mm stroker cranks and had no problems using the stock timing chain. The spacer thickness will depend on the deck height. Deck height is what determines amount of spacing needed. Most of my rebuilds leave with a .030 deck height and head shaved .025 giving the engine about 11:1 compression ratio, which can be run off pump gas although I do recomend 93 octane 89 is sufficient.