stroking?

[JDH]

I was on the web and found a web site. www.powroll.com. they will stroke a trx 450r motor. It talks about better mid range power like a big bore kit but with out the reliability problems. I s this true? Do you loose any throttle responce or top end pull? what about cost of this verses a big bore kit? I think said and done website said around $400. Any info on this? haven't rwally seen anything on stroker kits.

[jeepnrocks]

what do they do to the piston ? i dont like the idea of having something with a piston that i cant just replace easily

[JDH]

doesn't anyone have anything to say about this?

[chad502ex]

yea, my point is if your even considering seperating the cases to stroke, you might as well bore and stroke the limit. I mean why stroke 2mm when you can get 8mm?

anyone see my point?

Obviously, cost aside,....


chad502ex.com

[joe1l]

I've always thought of stroking to be the more unreliable method of getting more CC's and more power. The more you stroke the more unreliable it usually becomes. The stroker motors I've seen have all been nasty!! but this motor is an already stroked version of the CRF motor but with a smaller piston. When stroking is involved things like rod angle and piston side load become an issue. Plus a stroker will limit your ability to rev. A 2mm stroke is not huge but, in my opinion getting a larger piston would still be the more cost effective and reliable method.

[400ex4ever]

I agree with joe1l. I am personally going to go with the higher comp piston vice the stroker or big bore kit. At least for now.

[CdaleXtreme]

Grandma always said, "If you stroke it youll go blind!" :rolleyes:

[chad502ex]

Originally posted by joe1l
I've always thought of stroking to be the more unreliable method of getting more CC's and more power. The more you stroke the more unreliable it usually becomes. The stroker motors I've seen have all been nasty!! but this motor is an already stroked version of the CRF motor but with a smaller piston. When stroking is involved things like rod angle and piston side load become an issue. Plus a stroker will limit your ability to rev. A 2mm stroke is not huge but, in my opinion getting a larger piston would still be the more cost effective and reliable method.

piston loads are obstacles that are now easily overcome; especially, with ultralight oval piston that are manufactured today. For Example, my new JE +5mm Oval ultralight is lighter than the stock piston and even most big bore 500cc pistons, so the issue of slow-reving is irrelevant with my motor. I guess it really comes down to how much power one is interested in obtaining. I mean a slight bore may be considered more reliable, but would only give a fraction of power compared to a stroke/bore combination. No replacement for displacement.

Joe, i certainly understand your point and "to each thier own". For me it's simple,... I'd rather have 60-70hp for $3000.00 (which is ~double hp gain) over just bore ($300 for piston) that only gives me maybe 3-5hp.

Dollar to hp gain ratio is rougly the same for each. Cost isn't the issue for me, and reliablibility comparision is unpredictable. I turn the wrenches on my motor but if your the person who don't know how to build a motor then I would worry about stroking cause of the added cost to get a mechanic to repair for you if catastrophic failure occurs.

Also understand that I'm not arguing here, just providing another viewpoint as comparison. It's all fun here!

:D

chad502ex.com

[joe1l]

piston loads are obstacles that are now easily overcome; especially, with ultralight oval piston that are manufactured today. For Example, my new JE +5mm Oval ultralight is lighter than the stock piston and even most big bore 500cc pistons, so the issue of slow-reving is irrelevant with my motor. I guess it really comes down to how much power one is interested in obtaining. I mean a slight bore may be considered more reliable, but would only give a fraction of power compared to a stroke/bore combination. No replacement for displacement.
Joe, i certainly understand your point and "to each thier own". For me it's simple,... I'd rather have 60-70hp for $3000.00 (which is ~double hp gain) over just bore ($300 for piston) that only gives me maybe 3-5hp.

Dollar to hp gain ratio is rougly the same for each. Cost isn't the issue for me, and reliablibility comparision is unpredictable. I turn the wrenches on my motor but if your the person who don't know how to build a motor then I would worry about stroking cause of the added cost to get a mechanic to repair for you if catastrophic failure occurs.

Also understand that I'm not arguing here, just providing another viewpoint as comparison. It's all fun here!


Chad I do agree with you. I do feel though for the average consumer stroking would be a bit extreme. The oval pistons you are speaking of are new to me, my experience with stroked motors comes from the 2stroke motors. I myself would not mind a little stroke (no pun inteded) but what i have found is that engine builders don't seem to get the exact combination of stroke and bore size just right untill massive testing has been done. Sometimes the right combonitation of parts makes the motor reliable and fast. Being that 450R is still under a year old, i much rather wait it out and see what the killer combinations will be. The experementing with strokers begins now, when big bores and higher compression don't cut it.

[chad502ex]

Absolutely! The right bore/stroke ratio (or combination) is crutial to a motor being a slug or a thumper. It just so happens that "the king of cranks" aka Falicon (preferred Suzuki crank-house designer for the Hyabusa street machine) tested and proved that performance can actually decrease if the right ratio is not achieved on the 450r. Right now, there are engine builders out there who are boring and stroking to the max and getting backwards results (measured power actually decreasing) when going to far. Anyway Falicon indicated to me that optimum bore/stroke combo on the 450r is +2mm bore and +5.6mm stroke. I've decided to use a +5mm/+6mm ratio with an ultra-light piston thats lighter than Falicons +2mm. I think that weight reduction will make up for my +3mm over-bore. fingers-crossed.

Oval pistons are for piston side skirt load as the piston drags the cylinder wall. Oval piston help reduce the skirt drag on the engine front and back side of the piston. The bore is still round, its just the piston is slightly oval. Incredible concept.

chad502ex.com

[JDH]

d**n now that 's what I'm talkin about. Thanks for th einsight to both. much appricieated.

[450 Racer R]

how about something like a cylinder spacer? like something to place between the crankcase and the cylinder. would that do anything at all as far as performance? if everything else remained stock.

[BIGBLOCKBILL]

Does the slight oval shape of the piston effect ring seal or ring life? Are you doing any port work or carb changes? Let us know how the combo works out.

[chad502ex]

Originally posted by 450 Racer R
how about something like a cylinder spacer? like something to place between the crankcase and the cylinder. would that do anything at all as far as performance? if everything else remained stock.

installing a spacer, or thicker base gasket will do nothing to enhance performance; if anything compression will decrease and depending on the thickness of the spacer then timing chain length could be an issue.

chad502ex.com

[chad502ex]

Originally posted by BIGBLOCKBILL
Does the slight oval shape of the piston effect ring seal or ring life? Are you doing any port work or carb changes? Let us know how the combo works out.

no, the oval shape is only slight and can only be measured not really seen. I'm doing heavy port and flow work. I'm relieving my intake valves +2mm and my exhaust valves +3mm. Obviously, you would not want to put my head on a stock bore, the valves would punch the top of the stock sleeve if you did.

I should be putting dyno results together in about a month and will post on my site. I bet and hope to hit 65hp when I'm done. Afterwards, I'll be posting complete 550r building pictures and credit all my resources for thier hard work.

chad502ex.com