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  #1  
Old 22 Nov 2013
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Horsepower measured at the crank or rear wheel

Just a quick question but do bike manufacturers quote there bikes horsepower at their engines' crankshaft or at the rear wheel ?

On a dyno its the rear wheel so what kind of diffrence is there from readings stated on the crankshaft?
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  #2  
Old 23 Nov 2013
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Unless things have changed in recent years the manufacturers claims mostly come from power at the crank. Losses on the way to the back wheel vary but somewhere about 20% is the figure I have always worked with as rule of thumb (although it's been a while since I last had anything to do with dynos).

Measuring that power is another variable though as types of dyno, maintenance, calibration, climatic conditions etc all vary and have an impact on the numbers you get out.
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Old 23 Nov 2013
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So a KTM690 Enduro states it has a hp of 66 at the crank

KTM 690 Enduro*R 2014 - Highlights

but at the rear wheel it is 46.3 hp?


"This is one potent single. KTM
claims 63 crank hp at 7500 rpm. Our dyno testing yielded 46.3
rear-wheel hp @ 7250 rpm and 35.65 lb.-ft. of torque @ 6500
rpm"

http://www.mcnews.com/mcn/model_eval/2010JulyKTM.pdf

KTM 690 Enduro SMC Factory Pro 800 869-0497

So my DRZ400 its getting its wide ratio gearbox fitted shortly however it will also be close to 50hp at the rear wheel which will not effect its realiblity at all if done correctly as many people are getiing 40,000+ miles with this kit on

"Want 50hp out of your DRZ? Well, here ya go! This is our most common sold item for the Suzuki DRZ400. It includes all the items you need to put your bike up to 48-51hp at the rear wheel. All items are tested and developed by Eddie Sisneros. Contact us for discounted shipping options"

39mm "MX" FCR Carburetor (Tuned & Jetted)
94mm/440cc Big Bore Kit
Hot Cams Camshaft Set
SSW pipe


I was going the fit a +4mm stroker crank to make it to around 470 as i am spillting the case's anyway for the wide ratio gears however more work will then be needed to the head and also will need new stronger valves than the standard stock valves, to much into this build and also head gaskets blow so with the above mods it will run fine with no issues and i decided to go with another type of 94mm bore kit that has wider water jackets for better cooling. the drz400e has a slant body FCR carb fitted however there are know issues with some case of the vacuum plate breaking up and getting crunched up in the barrel smashing valves ect ect so i am going with the better 39mm "MX" FCR Carburetor (Tuned & Jetted)

The slant body carbs were stopped from being fitted to big production singles due to the vacuum plate being at an angle and all the intake suction presure being on the bottom of the plate, causing them to crack and fail in the long run,

Along time ago there was a rumored ''BIG'' dispute between ktm and keihin as there early 620 and 660 factory bikes were breaking the slides and causing valves piston and bore to end up in very very bad ways which wasnt cheap i believe even yam had a few problem with the early yzf400/wr400f with the same slide issue as why the only known bike to be produced with a slant body fcr after that period was the drz400E

Last edited by WesleyDRZ400; 23 Nov 2013 at 12:01.
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Old 24 Nov 2013
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They measure it at the crank...

Not only just because it's a higher number (sounds good for punters), but because it's a more reliable 'constant' and easily measured on a test bench.

A back wheel measurement has more contributing factors such as all the transmission variables, friction, etc. It is aways lower at the back wheel due to these factors also.
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  #5  
Old 24 Nov 2013
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Quote:
Originally Posted by *Touring Ted* View Post
They measure it at the crank...
Hmmm, I would say it's very hard to measure anything on the crank on most motorbikes.
Measurements are mostly done on the rear wheel and loss in driveline is calculated/estimated to give you "crank values".

Most supliers of powerparts are pretty optimistic
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Old 24 Nov 2013
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Quote:
Originally Posted by AliBaba View Post
Most supliers of powerparts are pretty optimistic
I agree however for my current mods i have seen Dyno sheet results of others who have the mods around 48-51hp

I will Dyno my bike in a couple of weeks
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  #7  
Old 13 Dec 2013
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My Triumph Explorer is said to make 135HP and I had mine dyno'd at an AMA race and it showed 125HP at the rear wheel (corrected).

Not a big loss but it does only have 11k on it.
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Old 16 Dec 2013
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Quote:
Originally Posted by moggi1964 View Post
My Triumph Explorer is said to make 135HP and I had mine dyno'd at an AMA race and it showed 125HP at the rear wheel (corrected).

Not a big loss but it does only have 11k on it.

Yes always a few HP difference on each Dyno run, i am dropping my DRZ off this week and after the work has been carried out it will be around 50hp at the rear wheel with a wider ratio gear box but lower revs though the range.

Its like a project that grew arms and legs, i like the DRZ but lacks power alittle and needs longer legs for the motorway runs

I could of brought a KTM 690 which is the better bike really but after all the work has been carried out this DRZ will still be cheaper than a 690 but its not really about cost more about i love the DRZ
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Old 16 Dec 2013
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A single cylinder 500cc drz would be a dream. Decent suspension and Fi and you'd have a champion.
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  #10  
Old 16 Dec 2013
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Originally Posted by *Touring Ted* View Post
A single cylinder 500cc drz would be a dream. Decent suspension and Fi and you'd have a champion.
Well looks like i will have to settle for a near 50bhp at the rear wheel DRZ-470cc with wide ratio gears, suspension work and a FCR MX carb for now then.........

Dropping it off in the morning so look forward to seeing how it goes

Guys getting 40k+ miles with this setup no work needed other than valve checks
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Old 16 Dec 2013
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Sounds awesome... I hope I get to see it at one of the meetings ????
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  #12  
Old 18 Dec 2013
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04 lc4 640, claimed 54hp,(Crank)46hp at r/w, opened up air box/ scorpion pipe/standard bst 40 jetted to suit, 52hp at r/w. I only mention this because if the 690 is only getting 46 at the r/w there is something wrong with it.
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Old 13 Jan 2014
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Other factors that can affect dyno readings include tyre type: a knobbly will cost you several HP as will a dry and poorly maintained chain.
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  #14  
Old 11 Apr 2014
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Just spoke to the dudes with my DRZ470 and the Dyno results so far are...

Before
Standard DRZ is 33.4 hp with torque at 25.6 lb·ft @ RW

After

DRZ is 40 hp with torque at 60 lb·ft. @ RW

So thats around 35 lb ft extra torque and 8 bhp!!!!

Pick her up next week
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  #15  
Old 11 Apr 2014
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That's a decent increase on a small bike. You'll feel that...

Keep the weight down and it will be even better..

Sent from my XT1032 using Tapatalk
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