RM-Z 250 Horsepower
Posted 11 March 2006 - 11:14 PM
99.9% of the time when you see actual dyno results of a motorcycle its rear wheel hp.
99.9% of the time when you see advertised hp of a new motorcycle its exaggerated by 10% or more.
When you read 34.5 on your title or in a magazine its a lie.
We have dynoed a RMZ250 so many times I lost count. I lost count in late 2003.
2004 RMZ250 29.5- 31 rwhp depending if u got a good one or not
2005 RMZ250 29.5- 31.5 rwhp depending if you got a good one or not
I have never ever seen a stock RMZ250 have over 31.5rwhp
RMZ250 with pipe and tweaked to the max. = 33-34.5rwhp
RMZ250 big bore and pipe( no other mods) = 36- 37 rwhp
RMZ250 big bore/pipe/cams = 37.5- 39 rwhp (depending on whether they were smoking out when they pressed the cam gear on or not)
RMZ250 port work by knowledgeable builder w/pipe = 35.5 - 37rwhp
RMZ250 port work/pipe/cams = 38-39 rwhp
RMZ250 big bore/port work/pipe/ waving the magic wand = 38.5-39.5 rwhp
RMZ250 big bore/port work/pipe/cams waving the magic wand= 39- 40 rwhp
RMZ250 big bore/stroker/port work/pipe/ no cams/waving the magic wand= 40-41.5rwhp
RMZ250 big bore/stroker/port work/cams/waving the magic wand= 40.5-41.5rwhp maybe 42 if you ran it on a Tuesday
RMZ250 big bore/stroker/port work/welded and reworked exhaust port/ pipe/ carb mods/ignition/ cams/welded and polished crank/ polished rod/ rem polsihed tranny (everything)/ceramic tranny and crank bearings/ ceramic wheel bearings/ceramic coated head,valves,exhaust port,piston, head pipe/ taking a screwdriver and prying the brake pads away from the rotor/ oxygenated fuel/leaned to the point of destruction/ adjusted ignition timing you got sick/ waved the magic wand/ said a prayer = 42.5-43.5 rwhp
No matter what hp your RMZ250 makes cold it looses between 1 and 2 rwhp when the oil temps gets above 250f.
No matter what hp your RMZ250 makes cold it looses between 2 and 3 rwhp when oil temps get above 300f.
The major variable in all the above dyno runs is whether we were drinking vodka or not.
Posted 11 March 2006 - 11:33 PM
I would save the cylinder for boring after you crash it. Its very likely that at some point you will either drop a valve or something that and ruin the cylinder. Then you can bore it.
Cams most of the time make good power. Some cams make the bike crank easier. I would do the port work before adding the cams or at least at the same time. Cams always work much better with a good head work.
Posted 12 March 2006 - 11:56 AM
Posted 12 March 2006 - 02:27 PM
The KTM definatly makes more power in stock form.
Modded out it all depends on who you have do the mods. The right engine builder can make any of the 250 4 strokes rip.
I am a much bigger fan of having a knowledgeable "hands on" engine builder do the work rather than some of the big name mass production engine houses.
Posted 13 March 2006 - 10:12 PM
I thought someone would catch it.
Posted 16 March 2006 - 04:08 AM
i.e hotcam worthwhile ? and porting ?.... high comp piston ? do the RM's live as close to the reliability edge as the CRF250's ?
my application would be enduro/cross country... so i'd like so low end snap... whilst maintaining some reliability... or am I a fool for going this route on one of these bikes ?
a great deal on a near new one has come up and I really don't know didely about them... I'd like to get the yz250f as i'm alot more familiar.. but i'd like to try something smaller and more nimble handling wise.... and something that doesn't have WP suspension
thanks for any help
Posted 17 March 2006 - 08:06 PM
Proper head work a will match hp with a big bore cylinder. HP delivery characteristics will be slightly different. I would also heep the compression close to stock.
Many times even on our practice bikes we will zero deck the cylinder also. Mainly to get the squish out of the bore. This also adds a small amout of compression. Depending on how much you have to cut the cylinder base.
With this set up you can run pump fuel and still makes lots of power.
Posted 17 March 2006 - 11:00 PM
Posted 18 March 2006 - 07:40 PM
If you are trying to make power you will need to have atleast a canister. I havent seen one aftermarket canister that doesnt make power. With porting alone you cant expect gobs of power.
The stock canister isnt desireable in any type of riding.
With porting and an exhaust this model makes good useable power. if the noise bothers you purchase ear plugs.
Posted 19 March 2006 - 07:40 AM
Posted 19 March 2006 - 02:32 PM
surely you can create great power without creating a loud exhaust note ? i'd have to say that even the FIM 96Db standard it too loud for use in public area's (judging by the public's feedback).
Posted 19 March 2006 - 04:40 PM
Posted 19 March 2006 - 08:31 PM
During testsing I noticed witht he sound level meter only 5 feet away a loud conversation in our shop can be in the 80db range.
Posted 19 March 2006 - 09:39 PM
I'm sure we won't have this problem when we're riding electric bikes
Posted 20 March 2006 - 12:01 PM
Posted 22 March 2006 - 10:21 PM
that's like a human convo!!! they make more noise than that snoring
They should baffle greenies snoring to 20 db. That way the suffocate and die