Gearing questions.

Jshipman81
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Jshipman81
Edited Date/Time 3/6/2014 6:11pm
How much does gearing selection play a role when it comes to porting and polishing a cylinder and head? I was reading some stuff Eric Gorr offers and he can change the cylinder to increase low to mid, mid to top end etc. I was also reading about taking .030" off the base of the cylinder to increase the low end. Lets say someone was looking for more low end power could you just add a tooth to the rear sprocket and get the same outcome? When setting up a bike, would it benefit more to gear the bike for top end power and then port the cylinder to increase the power to the low or mid of the power band? Also, lets say you send off your cylinder to your engine builder and spend a bunch of money on getting power to the low to mid of the powerband. When you get it back you switch back to the stock gearing (48t) before you were using (51t) and now you're disappointed because you cannot tell any noticeable difference besides reving longer and not shifting as much. Is it better to find a certain tooth sprocket and stick with that size when making adjustments to the engine itself? Would it benefit more to find a gearing that really has the low end you want and then send your cylinder off to get more top end? Or did I just open up a can of worms? Haha In my opinion, I would try to port a cylinder to increase performance throughout the powerband and only use gearing as a way to to move power from low to top end depending on track conditions and layout.
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Paw Paw 271
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Paw Paw 271 3/5/2014 6:03pm
3/5/2014 6:03pm
It all depends on which bike we are talking about, but in general try gearing before porting. Gears you can change, but once ported there is no going back without a lot of expense.

Paw Paw
Jshipman81
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Jshipman81 3/5/2014 8:32pm
3/5/2014 8:32pm
Sorry...2003 Honda Cr250. When selecting the right size sprocket is it best to ride the fastest section and base the gearing off of it? In my opinion, I would want to be in 3rd gear and just about to sign off, but enough there, so my engine isn't screaming before the corner. I've rode a local track where 2nd gear was screaming and 3rd was too low in the rpm's. In that instance, would it have been better to add a tooth to the rear sprocket, so I could get to 3rd sooner? Also, I've read a lot of posts where people are sending their cylinder in for porting and milling off .030" off the base before they even ride it. I would hope people would ride the bike first because each person rides differently and to just go off of what some other guy said worked for him is kind of brave. Just curious of other people's opinions.
Paw Paw 271
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Paw Paw 271 3/6/2014 6:54am
3/6/2014 6:54am
What sprockets are you using now front and back?
Jshipman81
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Jshipman81 3/6/2014 2:02pm
3/6/2014 2:02pm
It came with a 13 front and 51 rear. I tore my bike apart this winter because my frame was cracked and found another one on ebay. Once I got to tearing into my bike found out why my frame cracked. The lower two engine mounts were oblong, which put all the pressure up on the top frame mount. When I took the top end off I notice a hole in one of the reed petals and a crack in the cylinder right between the exhaust ports. That explains why it ran like crap the last time I rode it. I bought the bike used at the beginning of the summer last year. It ran decent, but had a bog down in the lower rpms. I just rode it like that because of what others have said about the TMX being a pain. Just reading up on stuff people on here have done and trying to educate myself.

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Paw Paw 271
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Paw Paw 271 3/6/2014 2:17pm
3/6/2014 2:17pm
At 13/51 you are geared a bit low right now, unless you are riding a very short track and then you could add 1 or 2 teeth to the rear sprocket to help. Until you get the carburation cleaned up, it will feel a bit under powered even with this gearing.
Jshipman81
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Jshipman81 3/6/2014 6:11pm
3/6/2014 6:11pm
Yes, you're right, but I was hoping I would get more of general answers to my questions. Is there a certain point where someone can say "hey, porting my cylinder for more low end will fix this problem over gearing selection"? Lets say I go to a new track, what section (starting straight, shortest section to a 90 degree corner, fastest section) would be the best to decide gearing? I was watching a YouTube clip of RC setting up Broc Tickle's bike for a race and he was telling the Yosh. Factory tuner what gear he was in and where. I would think he was trying to gear the bike for the least amount of shifting throughout the track. So do you focus more on top end power and burn through clutch plates like a teen girl goes through shiny lip gloss?

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