Size Up or Size Down?

[AliGee]

I've had a lot of experience on other powersport vehicles but don't have a ton of experience on dirtbikes.

I'm a 5'4" female and weigh around 145lbs? I live in Breckenridge, Colorado at 10,500ft so this bike will rarely go below 8,000ft. I will most definitely do a **** ton of trail riding, but I am not sure how much track riding I'll be doing.

I have been shopping for dirtbikes for quite some time, but never really found a bike that fit "perfectly". Today I came across a used KTM 105 sx and instantly fell in love. It was the PERFECT size and I feel the powerband would be right for me. I really love the idea of a 100 (105sx, kx100, CRF100R Expert).

However, that bike was $2700 and my max budget is around $1500. I want to buy used but it seems impossible to find 100's used. However, it's a piece of cake to find the 125's (kx 125, yz125) used, and it's also relatively easy to find used 85's.

I have also looked into trail bikes like TTR230, but unfortunately bikes like those are also impossible to find used, and I don't have the money to buy new.

If I had to decide between a used 125 or 85, which would be best for me?

I feel like the 125 seat height is too high (perfect is right around 34") and I also feel like it may be too much bike. I want to go for something small and fun... I don't need massive amounts of power. On the other hand, I've been told that an 85 won't be enough power...

I guess I'm frustrated. I'm not going to grow anymore and I know I'm a really awkward height to fit a bike. It's a huge bummer and I'm at a loss of which route to go... I'm 20 years old and I've wanted a bike since before I can remember. I really want to make it happen this summer. :(

Suggestions?

Thank you, thank you!

 

[IndyMX]

Before you discount the power of an 85, ride one... I was put on my ass several times by one, and I'm a whole person bigger than you..

 

[jb_dallas]

Its simple, if you are doing a ton of trail riding, you should buy a trail bike. I would avoid a motocross bike (YZ/CR/KX/RM 125 and the KTM SX [supercross] you suggested). Those are poor trail bikes because of lack of low bottom end power and the gearing is all wrong for trails...especially for a beginner. You might look at a CRF150, KLX140, or maybe a XR200 if they arent too heavy for you. The TTR, might be ok power wise, but again, heavy and not very agile.

 

[AliGee]

Its simple, if you are doing a ton of trail riding, you should buy a trail bike. I would avoid a motocross bike (YZ/CR/KX/RM 125 and the KTM SX [supercross] you suggested). Those are poor trail bikes because of lack of low bottom end power and the gearing is all wrong for trails...especially for a beginner. You might look at a CRF150, KLX140, or maybe a XR200 if they arent too heavy for you. The TTR, might be ok power wise, but again, heavy and not very agile.

Thanks for both the responses!

As I said, I would definitely LOVE a trail bike. I understand the wrong gearing for trails and the low bottom torque etc. I do have quite a few hours on smaller bikes, I've just never owned one...

The biggest issue I'm having is finding used trail bikes with a small budget. It's odd to me how popular the motocross bikes are up here in the mountains when we have so many mine trails, etc.

I will look into the KLX140 and XR200 and see if I can find any used around here... I have yet to find a CRF150.

But what I'm getting from IndyMX is that I would have plenty of fun on an 85 if I had to go the motocross route? I guess you also have to take into account the altitude, that kills a ton of power in my XTerra from sea level.

Again, thanks for the responses! I can't wait to become a REAL part of this online community! I've been itching for a bike since before I can remember.

 

[IndyMX]

Any bike is going to suffer at altitude, but jetted properly it should be just fine.

 

[Rich Rohrich]

If you can find a good deal on an 85 that you like it's a simple matter to convert it to an Offroad specific powerband SuperMini 100. It's pretty inexpensive and it would get you the best of both worlds without all of the expense.

Eric Gorr build tons of SuperMinis for shorter adults. Converting it only costs $400.
He explains it this way :

"Engine kits for adults riding supers are geared for off-road riding with a strong low to mid-range powerband that runs on pump gas. These engine kits are built for durability and easy starting."

Lots of good info in the link below :

http://www.ericgorr.com/superminis.html

 

[AliGee]

If you can find a good deal on an 85 that you like it's a simple matter to convert it to an Offroad specific powerband SuperMini 100. It's pretty inexpensive and it would get you the best of both worlds without all of the expense.

Eric Gorr build tons of SuperMinis for shorter adults. Converting it only costs $400.
He explains it this way :

"Engine kits for adults riding supers are geared for off-road riding with a strong low to mid-range powerband that runs on pump gas. These engine kits are built for durability and easy starting."

Lots of good info in the link below :



This sounds amazing, thanks so much!

 

[rmc_olderthandirt]

Any bike you get will need to be jetted for that altitude. There will also be a noticeable power loss so I would err on the high side.

My daughter is 22 years old, 5'2-1/2" (she always specifies the half) and a bit heavier than you. I recently bought her a Kx100 which fits her quite well. There are times that she could really use some more power but she has really surprised me on how well that Kx100 will get her up the hills.

I am from a slightly different frame of mind about two strokes being suitable trail bikes. I recently switched over to four strokes and I really love the low end torque but I also miss the agility of the two stroke.

There are several things that make a MX bike less than ideal for trail, some of which can be overcome. MX bikes typically don't have kickstands, which is fine at a track but a PITA when riding trails. Kick stands can be added, however.

A MX bike will usually have a close ratio transmission so that they can always be in the power band. Trail bikes tend to have wider ratio transmissions so you have a really low first gear for crawling over the gnarly stuff and a tall enough gear for screaming down the fire roads.

Wide ratio isn't something you can change, but you can change the overall gearing to suit your needs. If you ride a lot of dirt roads where going fast is necessary then knock a few teeth off the back sprocket. If you ride a lot of technical stuff where you need low speed torque then get a rear sprocket with a few more teeth (or drop one from the front sprocket).

I would recommend the KX100 or the KTM 105sx over an 85. I am sure you would enjoy the extra power and you get larger wheels, which can make a big difference when your picking your way over the rocks. I suspect that you don't need the seat to be any lower (100s are about 34", the 85s about 33).

You might also consider getting a 125cc two stroke or 250 four stroke and having it lowered. Choose a bike that has an 18" rear wheel (WR250F), drop the front forks as low as they will go, lowering link in the rear, shave the seat and you can end up with a seat height of around 35"

 

[AliGee]

That was definitely the best response yet, thanks!!

 

[FNG]

You will be down 30% on HP from sea level to 9K ft.

They also sell 85's in a big wheel configuration as well.