comparo
#1
05-08-2010, 07:15 AM
Join Date: Jun 2008
Location: So Cal
Posts: 1,353
comparo
This '84 xl250r honda kept right with the '09 klx250s thru the gears, same top speed too. If not for the '84s massive head shake I would have kept it for the wife. Lots of buyers remorse not seeing a brand new bike walk away from a 25 yo machine w/ 1600+ miles on it. 5 speed air cooled vs 6 speed liquid cooled...Trading bikes same results. Bogus
Gotta say thanks to Bill Blue for the 350 kit to make the anemic klx into a whole new bike. Way more low end torque off the very bottom and 8 mph faster on the top end (stock gearing). I'd say its in the 30s horsepower range. Forget lowering the c/s sprocket to a 13 it needs a 15.
Gotta say thanks to Bill Blue for the 350 kit to make the anemic klx into a whole new bike. Way more low end torque off the very bottom and 8 mph faster on the top end (stock gearing). I'd say its in the 30s horsepower range. Forget lowering the c/s sprocket to a 13 it needs a 15.
Last edited by RaceGass; 05-08-2010 at 07:23 AM. Reason: pic
#4
05-08-2010, 03:17 PM
It might also be possible that emissions requirements for motorcycles have tightened in the last 25 years. Perhaps noise too. Without a good EFI system manufacturers have to resort to lean mixtures and catalysts to meet emission requirements, which reduces power. It could be argued that the KLX put up some pretty impressive performance against a bike with very little or no such constraints.
*****Rant warning - Reat at your own risk***** I learned a little about this in college as an engineer and know enough to get myself in trouble. Just rambling off the top of my head.
A catalytic converter must have hot exhaust gasses to work correctly. Exhaust gas temperatures are controlled through the air/fuel mixture. A carburetor is actually a very crude method of feeding the proper air/fuel mixture to an IC engine as it only takes air velocity into account, using a venturi effect to draw fuel into the air stream. If you remember back to the '70's and early '80's cars had very low HP numbers for their displacement. Remember the 180HP 350cubic inch Corvettes? It was only with the advent of EFI that manufacturers were able to correctly map air/fuel ratios perfectly to maximize power AND keep the catalytic reaction at a level that satisfied the EPA. So in the later '80's and especially the '90's we started seeing big HP numbers from cars again. Oh yeah, a rich mixture would leave unburned hydrocarbons in the exhaust thus failing emissions and clogging the catalyst. The catalyst is there to take care of the oxides of nitrogen (NOx) that are produced when combustion is complete, at higher exhaust temperatures. Remember the old air pumps from the '70's? Their purpose was to inject air into the exhaust stream to help complete combustion of unburned fuel. Engineers were really scrambling to put band aids on the real problem back then, which is finding a way to control air/fuel mixtures precisely at all load conditions. Today, modern fuel injection, namely direct injection is so good that we see engines like the GM 3.6 liter doing 300+HP on 87 octane pump gas! Pretty incredible.
Unfortunately good fuel injection systems have not yet migrated to the big four dual sport bikes. Yamaha is the first to enter with the WR and from what I have read they are getting 5 or so more HP from that engine than team green is getting from the KLX out of the box. I would bet that the fuel injection is the key. And from the reports around the web from users even that fuel injection is pretty crude by current automotive standards. It is making more power and getting around emissions requirements but I have a feeling with a little tweaking 25+HP at the rear wheel is possible for 250cc dual sports. I think the WR is doing about 25HP now right? I bet there is another 3-5HP left in there IF the demand for such a bike was there.
In a strange way emission requirements are our friend in our pursuit of more power. Eventually carburetors won't be able to meet emissions no matter how lean the mixture or choked up the engine becomes. They will have to move to fuel injection and with that move we'll see big HP and better efficiency just like we've seen in cars. But like everything else it's all driven by money, or more to the point profit. They'll do it when it looks profitable.
So anyway I have a feeling your old XL is pretty much uncorked while the KLX is not.
- Mark
*****Rant warning - Reat at your own risk***** I learned a little about this in college as an engineer and know enough to get myself in trouble. Just rambling off the top of my head.
A catalytic converter must have hot exhaust gasses to work correctly. Exhaust gas temperatures are controlled through the air/fuel mixture. A carburetor is actually a very crude method of feeding the proper air/fuel mixture to an IC engine as it only takes air velocity into account, using a venturi effect to draw fuel into the air stream. If you remember back to the '70's and early '80's cars had very low HP numbers for their displacement. Remember the 180HP 350cubic inch Corvettes? It was only with the advent of EFI that manufacturers were able to correctly map air/fuel ratios perfectly to maximize power AND keep the catalytic reaction at a level that satisfied the EPA. So in the later '80's and especially the '90's we started seeing big HP numbers from cars again. Oh yeah, a rich mixture would leave unburned hydrocarbons in the exhaust thus failing emissions and clogging the catalyst. The catalyst is there to take care of the oxides of nitrogen (NOx) that are produced when combustion is complete, at higher exhaust temperatures. Remember the old air pumps from the '70's? Their purpose was to inject air into the exhaust stream to help complete combustion of unburned fuel. Engineers were really scrambling to put band aids on the real problem back then, which is finding a way to control air/fuel mixtures precisely at all load conditions. Today, modern fuel injection, namely direct injection is so good that we see engines like the GM 3.6 liter doing 300+HP on 87 octane pump gas! Pretty incredible.
Unfortunately good fuel injection systems have not yet migrated to the big four dual sport bikes. Yamaha is the first to enter with the WR and from what I have read they are getting 5 or so more HP from that engine than team green is getting from the KLX out of the box. I would bet that the fuel injection is the key. And from the reports around the web from users even that fuel injection is pretty crude by current automotive standards. It is making more power and getting around emissions requirements but I have a feeling with a little tweaking 25+HP at the rear wheel is possible for 250cc dual sports. I think the WR is doing about 25HP now right? I bet there is another 3-5HP left in there IF the demand for such a bike was there.
In a strange way emission requirements are our friend in our pursuit of more power. Eventually carburetors won't be able to meet emissions no matter how lean the mixture or choked up the engine becomes. They will have to move to fuel injection and with that move we'll see big HP and better efficiency just like we've seen in cars. But like everything else it's all driven by money, or more to the point profit. They'll do it when it looks profitable.
So anyway I have a feeling your old XL is pretty much uncorked while the KLX is not.
- Mark
Last edited by KE100; 05-08-2010 at 03:27 PM.
#6
05-09-2010, 01:04 AM
It might also be possible that emissions requirements for motorcycles have tightened in the last 25 years. Perhaps noise too. Without a good EFI system manufacturers have to resort to lean mixtures and catalysts to meet emission requirements, which reduces power. It could be argued that the KLX put up some pretty impressive performance against a bike with very little or no such constraints.
Mike
#7
05-09-2010, 01:55 AM
Join Date: Nov 2006
Location: Kennewick Washington, in the washington desert
Posts: 741
I had an 84 xr 250, one of the best trail bikes I ever had. The dual carbs acted like a 4 barrel a little hard to jet and the bike was touchy to start but performance was great.
#8
05-09-2010, 03:45 AM
When I was about 14 I had an XR75. I bought it used for $275. I think it was a 1976 model or somewhere thereabout. I loved trail riding on that bike. It wasn't fast but it had grunt for a little bike. I remember I could chug up, around, or through just about anything on that little bike. I had a few dirt bikes growing up and that was my favorite. After a few years I sold it for $250. I think I changed the oil once and cleaned the air filter. Bulletproof. Then again I never had a problem with my KE100 that followed the XR75 either.
- Mark
- Mark
