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Interesting to hear!

 

I have to tell you if you live in the east of the U.S. where trails are tight, or ride in sand that can be deep at times the 15/39 won't work well, Even the stock 14/42 is a shade high when the going gets really tough. The gearing really has to be set up for what you will ride. Fire roads will likely work well with the tall gearing, but get off on a somewhat muddy east Ohio hare scrambles track and you will likely end up replacing a burnt clutch. I ran a 15/39 and it would be great on roads and if mainly staying on fire roads, but when I went to Michigan to ride I had a 13/47 to make sure I had gearing that would get through deep sand without a lot of clutch slippage.

So if you get off on trails up in New York, you don't want to go overly tall. If you mainly do the dirt/gravel back roads without getting into serious mud or sand, the 15/39 will do the job though. In my area of eastern Ohio I'm running a 13/42 only because my chain is too short to run a 15/45. I wanted the 15/45 to have the ability to run about the same ratio as stock, but be able to drop significantly lower by going to a 14 or 13.

 

From the photos you posted it looks really hilly, so I'm surprised you find the cruising at 5600 RPM in 6th gear to be useful. Granted I have a 250, but with the stock sprockets I found 6th to be nearly useless, because if there's any incline you just have no usable power. Dropping a tooth on the front sprocket made it so that I could actually just put it in 6th and keep it there.

 

That is the important thing, a rider has to find what gearing will work for their road and trail use. If I did more open roads of any decent sort the 15/39, which is a 2.56:1 gear, would do okay. But when I knew I'd be in some serious sand I went to a 13/47, which is a 3.61:1, to be sure I wouldn't have to do much clutch slipping. My more normal riding is good with a 13/42, which is a 3.23:1, for where I play around. I don't care for using a really small countershaft sprocket, so when the next new driveline is needed I'm going to a 14/45, which comes in at 3.21:1. That gearing will also allow a 15/45, which is a 3.00:1, or a 13/45, which is a 3.46:1, stepping up or down with a change of the front sprocket. But again this was worked out by my kind of riding where I ride. Now the 15/39 allows one to step down to a 14/39, which is 2.78:1, or 13/39, which is 3.00:1, plus the gearing is on the 300cc bike, which has taller gearing than the earlier 250cc bike reflecting the added power of the 300. So the taller gearing works well with the 300 where the 250 wouldn't do so well - and yes that 50cc can make that much difference. I was totally surprised how much difference a 27cc change made when I did a bigger bore on my KLX650, so I have to think the step from 250 to 300 has to be pretty good.

I have run the 15/39 on a 250 and it worked great for more road use and some of the off road I do, as it is working for @Olderider and the reason he is using it. If I remember right, Olderider is located in the Pacific Northwest and the fire roads are common out there and it's more open than in the east here, so what works there may not be good for here in the hills/mountains of the east, and vice versa for the mountains of the west. But it is good to get information out for what works well where and then a rider take note from those comments. Gearing preference or need is far from universal. .

 

@klx678 so the gears in the transmission are actually taller in the 300 than the 250? Also it's not even 50cc, its only 43cc more for the record.

 

I do not know about the gear box, but the 300 uses a 14/40 where the 250 was using a 14/42.

Maybe you missed my comment about how much difference there was with a 27cc gain on a 650? I was rounding. Even at "only 43cc" that is a greater boost than the 27cc on my 650. If you consider it against a 250cc displacement that is 17% increase in displacement. That is a serious gain.

 

Interesting about the smaller rear sprocket on the 300. I would have thought Kawasaki was going for really trying to improve acceleration compared to the 250, not trying to stretch it's legs.

I read your 27cc comment loud and clear and I hear what you're saying. 17%, as a percentage alone, is a nice statistic. But 17% of very little to start with still isn't that much.

 

I'm just here to start arguments, really? Weighing the pros and cons of modifications to our platform is arguing?

 

@greychinos and @Olderider Don't let anything bother you in forums. Print is never as good as an actual conversation. You can't tell sincerity from sarcasm or actual inquisitive nature versus testiness. Plus we all get a bit wonky at times, I definitely do. It is easy to be taken the wrong way or misunderstood.

I will say I only commented on the gearing because it is so personal to the nature of use, pure discussion. Nothing more was intended.