250r longrod advantages?
Feb 8, 2003 | 02:34 PM
#2
Trailblazer
Joined: Jul 2002
Posts: 83
Likes: 0
250r longrod advantages?
The reasons I heard honda went to the long rod were:
1) More reliable? I think my 86' is pretty reliable, so I am not to sure on that one.
2) It was supposed to make the power less peaky. Just to smooth out the power-band.
1) More reliable? I think my 86' is pretty reliable, so I am not to sure on that one.
2) It was supposed to make the power less peaky. Just to smooth out the power-band.
Feb 8, 2003 | 02:52 PM
#3
Trailblazer
Joined: Jul 1999
Posts: 77
Likes: 0
250r longrod advantages?
A big reson is price. When I replaced my crank the short rod was quite a bit more costly than the long rod. Just remember that you have to use a spacer plate if you use the long rod and an '86 style piston.
Feb 12, 2003 | 11:05 PM
#7
Pro Rider
Joined: Nov 2001
Posts: 1,631
Likes: 0
250r longrod advantages?
Originally posted by: DaBeechMan
Im not allowed to help any of you guys now. DevilMan says im a know-it-all. So he can help you from now on.
Im not allowed to help any of you guys now. DevilMan says im a know-it-all. So he can help you from now on.
LOL!![img]i/expressions/face-icon-small-happy.gif[/img]
Yeah, you "know it all"![img]i/expressions/face-icon-small-disgusted.gif[/img]
Trending Topics
Feb 13, 2003 | 04:32 AM
#9
Extreme Pro Rider
Joined: Oct 2002
Posts: 4,433
Likes: 0
250r longrod advantages?
"Practical experience tells me that a shorter rod will out perform a longer rod.....except in longivity!
In my opinion, the difference seems to be more in "when" the piston speed is different.
The long rod does have more dwell time around TDC, and that probably does translate into a more efficient burn of the fuel charge. The push is going to be through a less servere rod angle, so it will be easier on the piston and cylinder wall during the powerstroke. The fact that the long rod moves slower in the upper quadrant, should also give you a more efficient burn, because you will have more time for the burn to happen, and more time to translate that burn into rotational force upon the crankshaft. The down side of the long rod seems to come in because it is faster during the lower quadrants than a short rod. Because it started slower at the top, it must move faster at the bottom, when the fuel is being transfered up into the bore area. It is not very easy to see, but the piston will be over 1/2 way down the cylinder when the crank is at 90 degrees, and this is where it starts getting faster. As you may have noticed, the faster speed at BDC is quite noticable, and this is when we are transfering the charge.I believe we will find that the transfer Timing Area (TA) is less with a long rod motor, due to the fact that we have the same size ports....but less time for them to get used! The slow speed in the upper quadrant will most likely hurt performance when the charge is getting compressed, it should be more benificial to compress the charge faster. This may be part of the reason a long rod motor seems somewhat "lazy" or "soft" off of the bottom end."
This should explain it better
In my opinion, the difference seems to be more in "when" the piston speed is different.
The long rod does have more dwell time around TDC, and that probably does translate into a more efficient burn of the fuel charge. The push is going to be through a less servere rod angle, so it will be easier on the piston and cylinder wall during the powerstroke. The fact that the long rod moves slower in the upper quadrant, should also give you a more efficient burn, because you will have more time for the burn to happen, and more time to translate that burn into rotational force upon the crankshaft. The down side of the long rod seems to come in because it is faster during the lower quadrants than a short rod. Because it started slower at the top, it must move faster at the bottom, when the fuel is being transfered up into the bore area. It is not very easy to see, but the piston will be over 1/2 way down the cylinder when the crank is at 90 degrees, and this is where it starts getting faster. As you may have noticed, the faster speed at BDC is quite noticable, and this is when we are transfering the charge.I believe we will find that the transfer Timing Area (TA) is less with a long rod motor, due to the fact that we have the same size ports....but less time for them to get used! The slow speed in the upper quadrant will most likely hurt performance when the charge is getting compressed, it should be more benificial to compress the charge faster. This may be part of the reason a long rod motor seems somewhat "lazy" or "soft" off of the bottom end."
This should explain it better
