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HeadTrauma

Gaining power, but also maximizing torque?

10 posts in this topic

It seems that cars and motorcycles these days are increasingly skipping on the torque in order to make big power numbers at high rpm. Since an aircooled XR is somewhat limited by design and dont like to be revved to death, I thought it would be cool to build it to not only make more power, but moreso impressive torque. My automotive engine building experience has taught me that you can run big valves and ports with a somewhat small intake and get about equal gains in power and torque.....relying heavily on the right cam grind. Since a diesel bike isnt in the near future and my diesel Dodge isnt either, here are my thoughts;

A few mods that come to mind are bigger valves and just a light port cleanup, 10:1 compression(640cc if necessary), and a midrange oriented cam. I already have most of the other parts. Any thoughts or suggestions?

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Epoxy coat the intake ports for more velocity. Do the squish. Lighten and balance the crank. Knifedge. Tighten up valve clearances (not recommended for the faint of heart)....just remember the bike is gonna run strongest just before it goes BOOM!!!! LOL

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From what I understand, there's very little material left with the use of the bigger valves on the xr650r head and further valve work may or may not be possible. It's quite possible that when it comes time for a valve job, you may end up buying a new head if you were running big valves.

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From what I understand, there's very little material left with the use of the bigger valves on the xr650r head and further valve work may or may not be possible. It's quite possible that when it comes time for a valve job, you may end up buying a new head if you were running big valves.
Since an aircooled XR is somewhat limited by design and doesn't like to be revved to death, I thought it would be cool to build it to not only make more power, but moreso impressive torque.

How about a 600R then? In my sig.....

Anyway, being a dry sump engine, I wouldnt think knife edging the crank would do much for power. Also, building for torque doesnt mean sacrificing reliability. If anything, it should improve longetivity unless some crazy compression is used. I like the idea of a fully built 50hp XR600, but I find myself using the bottom and midrange the most. If I have to use a 660 kit or even a bigbore and 650L crank and a custom cam to get monster torque, I will. Anyone else?

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There is a company in England converting the KLR 650 to diesel. They save the trans and scrop the rest. Built an all new diesel on top of the factory trans. How about that for torque. The site I read said 120 mpg and it has a 6 gallon tank on it. They are making them for the US Marines. It also said it is not much louder than a stock KLR. I just do not like the color, olive drab. If I can remember what I did with it I can post the site.

Ray

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http://www.motorbikestoday.com/features/Articles/diesel_bikes.htm

You might want to consider a dual spark plug head for your torque monster...there was an article in one of the Harley type mags recently that went on and on and on about putting a second spark plug in high torque motors...got me thinking about how cool that mod would be for the big XR/XL's...

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Dont sweat it, I've seen the article. Thats what I had in mind when I said "a diesel bike isnt in the near future". Nothing on the market and no surplus KLRs yet.

I've also seen the 650R turbo Dakar bike.

Also, show me a company that makes a dual plug head for an XR600 and I'll give you $100. Besides, I think more could be gained by ditching the RFVC hemispherical combustion chamber for a pent-roof with more quench. Luckly the 600 is aircooled so a billet head could be made more easily than one with water passages. If I had all the time in the world and a Haas CNC mill I would try that.

Well, its looking like a bigbore kit and (possibly)custom cam are where the hope lies. If I ever get my hands on a setup, I'll try fuel injection too.

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You want off the shelf stuff?

Yeah--ok--its been done a number of times on here before--but some work better than others...

Heres my torque monster:

680 piston--custom 10.25:1 compression

machine balanced crank with oversize bearing

kibblewhite SS exhaust valves with deep seat work

kibblewhite Ti intake valves

HRC heavyduty camchain, guides, gear

hardened rocker arms

mid grind cam

carilo rod

kibblewhite HD springs

40x42mm Edelbrock pumper carb

something similar on your XR600 would work well. hope that helps you.

pumper carb with dual spark plugs is gonna cost ya $7-800--and yeah for $100 i will put you in touch with engine builders who can do it...going with FI is gonna cost ya big bucks. mapping a custom FI system could easily take 3-4 months and cost thousands....i went thru it on a BMW Dakar bike--major pain in the butt.

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You want off the shelf stuff?

Yeah--ok--its been done a number of times on here before--but some work better than others...

Heres my torque monster:

680 piston--custom 10.25:1 compression

machine balanced crank with oversize bearing

kibblewhite SS exhaust valves with deep seat work

kibblewhite Ti intake valves

HRC heavyduty camchain, guides, gear

hardened rocker arms

mid grind cam

carilo rod

kibblewhite HD springs

40x42mm Edelbrock pumper carb

something similar on your XR600 would work well. hope that helps you.

pumper carb with dual spark plugs is gonna cost ya $7-800--and yeah for $100 i will put you in touch with engine builders who can do it...going with FI is gonna cost ya big bucks. mapping a custom FI system could easily take 3-4 months and cost thousands....i went thru it on a BMW Dakar bike--major pain in the butt.

Thats the kind of setup I'm looking for. :cry: Does a pumper carb really help, or does it mainly improve transition from light to heavy throttle? How long do those Ti valves last? Also, what do you think of Extrude Honing, or is hand porting better?

I think I have a turbo in the garage small enough to work......

I didnt thing you were serious about a dual-plug head :cry:. Can it actually be done on an XR600?

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