Ttr90 motor build

[Randy K]

50 minutes ago, FEAR VENOM said:

 

I understand that you need as much power as possible to clear tabletops but im going to recommend again a bore up kit, these small motors handle the extra power very well and generally can be had for fairly cheap and with low maintenance, if you really want to keep up with your friends on a 90cc your going to have to revs the living hell out of the motor. Tbolt usa has bore up kits with carbs and high compression pistons with a cylinder jug for cheaper then the combined price of you individual parts. Also might be good to look into an aftermarket cdi box to get a more aggressive power curve and timing. The best way to keep up is displacement and if im not mistaken your bike can go up too 125cc range without loosing reliability

[FEAR VENOM]

1 hour ago, Randy K said:

I understand that you need as much power as possible to clear tabletops but im going to recommend again a bore up kit, these small motors handle the extra power very well and generally can be had for fairly cheap and with low maintenance, if you really want to keep up with your friends on a 90cc your going to have to revs the living hell out of the motor. Tbolt usa has bore up kits with carbs and high compression pistons with a cylinder jug for cheaper then the combined price of you individual parts. Also might be good to look into an aftermarket cdi box to get a more aggressive power curve and timing. The best way to keep up is displacement and if im not mistaken your bike can go up too 125cc range without loosing reliability

I was gonna do a 110 big bore but they don’t make a cylinder sadly anymore from tbolt takegawa or any other brands and I’m not gonna settle for a chinese head or bore out my stock head and have it wicked thin and in reliable. If take gawa or tbolt still made a cylinder I’d jump right on it but sadly they sell everything but the cylinder so it’s not really an option.

[Ud_Luz]

17 hours ago, Randy K said:

I have tried xylene which is a paint solvent and has an octane rating of 117 with 4 gallons of non ethanol fuel and 1 gallon of xylene to get in the 105 range but my bike is 12 to 1 compression so anything over 100 octane doesnt help me sadly. Old F1 cars ran on fuels that were 70% xylene+acetone blends with gas mixed in for 30%. I nerd out a little when it comes to homemade dino juice blends, my personal hobby

I used to run that mixing Buick Grand Nationals. I'd use 2 oz of Marvel Mystery oil per 5 gallons to replace the oil washing around the piston from xylene or toulene.

[Heikki1]

Buy a KX65. I just sold my ttr90 and bought a KX65. The KX is a beast compared to the ttr. Every time I get on it I smile ear to ear. Then my 8 year old tells me to get off his bike. 

[FEAR VENOM]

Just now, Heikki1 said:

Buy a KX65. I just sold my ttr90 and bought a KX65. The KX is a beast compared to the ttr. Every time I get on it I smile ear to ear. Then my 8 year old tells me to get off his bike. 

Haha yeah my younger brother had a 65 awhile back and I’ve rode around on it def a fun little bike buh not really a pitbike and like I said sellinh isn’t really an option 

[mbrick]

I don't think you are going to get there with a cam and bumping the compression... the 110 is 22% more displacement.

As others said you would be better off selling the 90 and picking up a 110.  The MSRP is only $2499 for a 2021 CRF110.

[SoCal Head Grinder]

The TTR90 head does respond to a little porting and a better valve job but still it and the valves are on the small side to make a significant increase in top end power.  You can make the bike a lot more fun and capable but it will still not be the same as a 110.  The new CRF110 have roller rockers and fuel injection!

Edited November 19, 2020 by SoCal Head Grinder

[FEAR VENOM]

1 minute ago, SoCal Head Grinder said:

The TTR90 head does respond to a little porting and a better valve job but still it and the valves are on the small side to make a significant increase in top end power.  You can make the bike a lot more fun a capable but it will still not be the same as a 110.  The new CRF110 have roller rockers and fuel injection!

Yes the new Honda’s are bad ass my brother had one for a few months we put a pipe and tall bare on his and that thing was a blast on the mini track. I like my 90 tho and don’t have the option to really sell sadly so gotta make do with what I got l!!!

[FEAR VENOM]

8 minutes ago, mbrick said:

I don't think you are going to get there with a cam and bumping the compression... the 110 is 22% more displacement.

As others said you would be better off selling the 90 and picking up a 110.  The MSRP is only $2499 for a 2021 CRF110.

As much as I’d love to get a new 110 selling my 90 isn’t really much of an option, so I gotta make do with what I got.also gonna add a fmf exhaust to it and a uni flo filter an over sized carb and the porting high comp piston and bigger cam should all come pretty close to a 110 power out put is not far off from the factory I think I can make it happen. If not then maybe I will consider boring over to 110cc and using a 52mm high comp but boring isn’t really my favorite choice 

[mbrick]

It might come close to a stock 110... but if any of your buddies on a 110 also have a cam and piston and exhaust they are that much further ahead.

I don't know that much about a TTR90 but is the stock carb a bottleneck?  The oversize you listed is $$$.  And it may reduce signal.  Bigger does not always mean better.

I wouldn't spend all that money on a 90 to only come close to a 110, but that's just me.

[FEAR VENOM]

Just now, mbrick said:

It might come close to a stock 110... but if any of your buddies on a 110 also have a cam and piston and exhaust they are that much further ahead.

I don't know that much about a TTR90 but is the stock carb a bottleneck?  The oversize you listed is $$$.  And it may reduce signal.  Bigger does not always mean better.

I wouldn't spend all that money on a 90 to only come close to a 110, but that's just me.

All my buddies wouldn’t ever think of touching a motor their parents but then a brand new klx110L every two years with a two year warranty they keep thier pro taper tall bars and thier pro circuit exhaust and slap em on every two years (must be nice) I have to pay for everything sadly so I new 110 would be a big hurting on my bank account as a senior in high school,anyways as long as I have a little more pepper out of the 90 I’d be happy I’m not looking for the next greatest mod bike jus sum  that’s gonna pull a little harder out of corners and every time my buddy hops in the skid steer it’s not don’t make it to big it’s go with the flow. 

[mbrick]

What is the total you are budgeting to spend on the 90?

Only you can make the decision if it's a good idea (sounds like you have) but I would look over the numbers more first.

[nicksdade]

It’s easy to get more power out of these little bikes. 90 and 110 makes a huge difference with fmf exhaust,mild porting and rejetted carb. Did this to both and my boys rode the hell out of them. Side note t4 is direct pump gas replacement. Run t4 in everything even lawn mower. U4 for mildly ported engine 

[FEAR VENOM]

6 minutes ago, mbrick said:

What is the total you are budgeting to spend on the 90?

Only you can make the decision if it's a good idea (sounds like you have) but I would look over the numbers more first.

Yeah that’s the thing most of these parts are gonna be Christmas gifts so it’s not all coming out of my pocket, I have split parents so they give me a set budget every year and let me buy stuff so I ordered up all these parts and lots more, I can’t take the cash and pocket it and put it towards a 110 so that’s why I’m stuck with the 90. Here’s 90% of what I ordered.

[Randy K]

3 hours ago, Ud_Luz said:

I used to run that mixing Buick Grand Nationals. I'd use 2 oz of Marvel Mystery oil per 5 gallons to replace the oil washing around the piston from xylene or toulene.

Marvel mystery oil is my go to as well too, i have thought of messing with toulene but never bought any as of yet,xylene+toulene+acetone+mmo sounds fun to try as long as i can get anhydrous base chemicals again... Still have some 10% acetone 5% xylene mix i got to go through before my next experiment

[Dirtymutt9]

if you want to make power in your mini bike t4 isnt going to do much. 

I used to be hard into minibikes about 10-15 years ago. the fuel you want to use is MR12. you have to jet specifically for it and cant leave it in the bike but you will see at least 5% more power JUST FROM THE FUEL. if you raise compression you will get even more power but you cant go too high as the fuel is only 96-98 octane. 

We used to run it in stock crf50s with no engine mods except larger jets and it was a significant difference in power. FYI its almost 30 a gallon! BUT IT WORKS!!!

[FEAR VENOM]

1 minute ago, Dirtymutt9 said:

if you want to make power in your mini bike t4 isnt going to do much. 

I used to be hard into minibikes about 10-15 years ago. the fuel you want to use is MR12. you have to jet specifically for it and cant leave it in the bike but you will see at least 5% more power JUST FROM THE FUEL. if you raise compression you will get even more power but you cant go too high as the fuel is only 96-98 octane. 

We used to run it in stock crf50s with no engine mods except larger jets and it was a significant difference in power. FYI its almost 30 a gallon! BUT IT WORKS!!!

Finally sum good info feel like I’ve been argueing with everyone responses like this are what I’m looking for first responders major motor build and these are the tips in looking for thank u will def read up on sim reviews and call my dealer to see how much a gallon I will pay!!!

[Dirtymutt9]

8 minutes ago, FEAR VENOM said:

Finally sum good info feel like I’ve been argueing with everyone responses like this are what I’m looking for first responders major motor build and these are the tips in looking for thank u will def read up on sim reviews and call my dealer to see how much a gallon I will pay!!!

it only comes in 5 gallon pails.

Most people have no idea what they are talking about when it comes to race fuel. octane is only one aspect of it and everyone seems hell bent on telling people they dont need it, lol

If you do choose to try the mr12 start with going 2 sizes larger on the main jet and one on the pilot. its really hard to read plugs with so you will have to tune by feel. on the crf50s we'd jet up 3 sizes from stock. 

if mr12 is too expensive u4.4 works well but only makes about half as much power in a non high compression bike but the difference is still pretty noticeable. 

have fun!

[Ud_Luz]

I'm trying to get my mind wrapped around $30 a gallon fuel for a 6 or so horsepower engine.

I went through 50 gallons last riding trip. That'd be $1,500 in fuel.

Seems to me it would cost less money to get a more powerful bike. I had my kids on ttr 110's and then put them on KX 65's, the difference between a skateboard and the Millinium Falcon. 

 We went to Colorado and they didn't have enough power to ride hardly any trails there on the ttr's.

Not to upset anybody but what am I missing here? The ttr is an awesome small trail bike, awful race bike.

[FEAR VENOM]

1 hour ago, Ud_Luz said:

I'm trying to get my mind wrapped around $30 a gallon fuel for a 6 or so horsepower engine.

I went through 50 gallons last riding trip. That'd be $1,500 in fuel.

Seems to me it would cost less money to get a more powerful bike. I had my kids on ttr 110's and then put them on KX 65's, the difference between a skateboard and the Millinium Falcon. 

 We went to Colorado and they didn't have enough power to ride hardly any trails there on the ttr's.

Not to upset anybody but what am I missing here? The ttr is an awesome small trail bike, awful race bike.

That’s the beauty of pitbikes their horrible race bikes and that’s the point . I ride once every Friday night from 7-10 under the lights with my friends I didn’t even burn 5 galleons all season. Now when it comes to full size 450 I ride twice a week for a lot of time and race the weekends.