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Any horsepower predictions?

24 posts in this topic

04 650 L

Wiseco 10.25 : 1 piston 100mm

Hotcam stage 1

Carrillo rod stock stroke

Mikuni TM 38mm Flatslide

UNI filter

XR's only headpipe

Yoshimura exhaust

Custom airbox / plenum

Custom port and polish Cylinder Head job

I will be breaking the motor in on an engine dyno with wideband o2 sensors so the carb will be jetted correctly. I will then put the motor in the bike and get some RWHP numbers :thumbsup:

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i say plus 8 from whatever your baseline is.

It would be more than 8 hp but I didnt baseline the motor:ride:

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It would be more than 8 hp but I didnt baseline the motor:ride:

how do you know how much it is going to be.. isn't that the whole point of you putting it on the dyno. if 35 is your baseline and you gain 8 that is some serious gains. something like 22% i don't have a calculator but i think it is close to that. how much do you think you will gain?

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04 650 L

Wiseco 10.25 : 1 piston 100mm

Hotcam stage 1

Carrillo rod stock stroke

Mikuni TM 38mm Flatslide

UNI filter

XR's only headpipe

Yoshimura exhaust

Custom airbox / plenum

Custom port and polish Cylinder Head job

I will be breaking the motor in on an engine dyno with wideband o2 sensors so the carb will be jetted correctly. I will then put the motor in the bike and get some RWHP numbers :thumbsup:

56 HP and 55 lb/ft of torque. But not for long if you are running it in hot temps. Maybe you can design a water cooling system for it :thumbsup:

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That's not a big bore, just a higher comp piston and lumpy cam right?

The XR650R runs ~45-48HP uncorked. The 650R uses a 10:1 comp piston. I thought the 9:1 comp piston 650L made quite a bit less HP. I would say that the new mods should put you in the stock uncorked 650R range of 45-48.

I would strongly recommend installing an oil cooler (like on the XR400) for this mod. Good luck, let us know how it goes.

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One other thing, the 650R uses a 40mm carb. I would think with those mods and the top end cam that you would have better results with a 40mm rather than the 38mm carb.

I run the Mikuni TM40 on my 650R and have played around with jetting a bunch. I would be really interested in hearing the details of your final jetting setup with the 38mm Mikuni. For example, I run a 25 pilot, 1.2 air jet, Y-6 needle jet, 9DJY4 needle on the 3rd clip position and a 145 main jet.

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Why do people change con rods? Unless the stock rod is worn out, I see no benifit. The engine won't make enough power to hurt the stock rod.

I am always amazed at the number of people that respond and suggest heat problems. Do any of you even have a high comp piston? My bike never gets over 225F at 90+F ambient. An open exhaust and correct jetting have more to do with engine temperature than a mild bump in compression (stock compression is 8.3:1 by the way). 91 or better gas works fine, no race gas needed.

You will get high 40s to low 50 with this engine config. The engine will make very little low end torque. You can forget about first and second gear power wheelies unless you wind the crap out of it. It will rev out much easier and has a good top end hit, great for supermoto and street riding.

To get more power you will need a more aggressive cam, Hot cams is one of the least aggressive. Shorter valve guides and springs. Larger valves and a three angle valve job. More aggressive cams will require the engine to be rev'd higher to get maximum power. The counter balancer has been known to slip in its press fit with sustained high rpms. If this happen the engine is junk as the balancer will slam into the con rod and destroy the cases and lower end.

I would have chosen a pumper carb over the TM for a little faster acceleration, but they are close to twice the cost.

Good luck, I will be interested to see the dyno sheets.

MGS

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Hey MGS781,

You are the one with the sweet looking 650L SM right? Nice job by the way. You are always vocal about the L, keeps balance in the world from the over inflated R owners egos ; )

Thanks for the correction on the L's compression ratio. I agree that proper jetting goes a long way to maintain a good engine temperature.

My point was that any cooling benefit is a good thing with any motor, especially air cooled motors and when trying to squeeze out more power. I've owned an XR200 and XR400. Both air cooled, and I've felt the heat on my legs while riding, especially when the going gets slow on trails and such. The XR400 had a nifty oil cooler up under the headlight. Not only will it increase the oil capacity, it will keep the oil cooler and make it last longer, offering better/longer lubrication and durability of the newer motor. I've heard that other L owners have added oil coolers with good results. It's kinda like insurance. You don't HAVE to have it, but it sure is nice when you do need it.

Ride ON!

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04 650 L

Wiseco 10.25 : 1 piston 100mm

Hotcam stage 1

Carrillo rod stock stroke

Mikuni TM 38mm Flatslide

UNI filter

XR's only headpipe

Yoshimura exhaust

Custom airbox / plenum

Custom port and polish Cylinder Head job

I will be breaking the motor in on an engine dyno with wideband o2 sensors so the carb will be jetted correctly. I will then put the motor in the bike and get some RWHP numbers :thumbsup:

Just curious as to why you chose the L to begin with. I also have an 04 L.

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Probably the same reason I did, because it is street legal out of the box.

Different states and countries have different rules about converting offroad bikes to on road. I know it has been done in my state, but I wasn't willing to risk it.

Would you want to spend 6 grand on bike just to find out you can't register it for street use?

MGS

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That's why I chose mine too, even though I can plate a R. The cost is what made up my mind.

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On an old YAM XT500 1981. I kept stock bore but upted the comp & a med cam . reground valves & new springs & seals. The beast ran strong but real hot. (always checking right boot ( felt like it was on fire and gas would litterally boil in the alum tank) BTW jetting was on. (My .02)

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Just curious as to why you chose the L to begin with. I also have an 04 L.

I bought it new in 04 and started playing with it. Then a small spring in the tranny broke. I had to split the cases to get it and fix it. So i figured it was a good time to upgrade the motor.

The rod is a little lighter and alot stronger. I just wanted added strength.

As far as the cam goes I would like to upgrade to a more agressive profile. Hardened rockers would be manditory. Basically when im ready to get my rockers hardened or buy new ones i will change the cam again.

I will post dyno graphs FOR SURE. :thumbsup:

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I'd also be interested in your gas mileage befroe and after. I'm getting around 46mpg on the street with a UNI filter, 15/48, 140/80 rear tire, E-series.

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[i hate to be the bringer of bad news, but if you get 42hp off the back wheel of an L with those very mild mods you will be totally lucky. The L motor needs to be very modded, like big bore, hot cam, hot CDI box, porting, velve job, and so on to get up to the high 40s low 50 in RWHP. You can't compare that motor to a XR650R either because they are totally different motors. Id say if you install a Keihin FCR41 youll notice it where it counts...seat of the pantaloons, I have a 1996XR600R that has a pipe, jetting and a stage one hot cam, Im doing a hot box CDI, and some mild porting, I had it dynoed, with just the pipe, jetting and cam, and this is at 5280ft from sea level and it has 40.2 rwhp. I may do a 610cc or 630cc kit with only 11:1 compression so itll be as easy to start and take pump gas.

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