Best gearing for fmf?

mjgnslngr

mjgnslngr

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<<Newbie! so excuse me if this question has been asked before. ive searched it and didnt turn up much for answers so i thought id check here.

so, ive read alot that fmf is an "ok" exhaust for a blaster. the problem lies in the low-end.(not much) id like to ask those of you with fmf knowledge whats the best gearing for a basic blaster. not a mx or hard core rider, just some trails and the occasional rip in the pit. (with mild up grades "jetted-270, boyeson power reeds, 18" rears, uni filter and no air box lid) would most say 13t front but not much on axle gearing? any combo that anyone has tried that worked better than the 13/40 or 14/40???

im trying to work with what ive got, and ive read alot about how fmf sucks in the low range. just thinking of ways to improve the 'Waaaaa' factor. chime in, any help would be a gift, thanks.
 
that fmf should be providing you plenty of bottom end, and mids, thats where the fmf shines, if you read it lacks bottom end, those are false reports
the top end is where that pipe slacks
is it possible your bike already has 14/40 gearing ??
13/40 should be perfect, and even more low end coupled with the 18" tires
i say you have other problems ?
hows the carb?? good and clean ?,
filter clean ?
airscrew adjustment ?
what fuel/oil mix you running ?
how's the compression ?
or maybe your just expecting more than a stock motor blaster can provide ?
time to get that thing ported !
 
awk08 said:
that fmf should be providing you plenty of bottom end, and mids, thats where the fmf shines, if you read it lacks bottom end, those are false reports
the top end is where that pipe slacks
is it possible your bike already has 14/40 gearing ??
13/40 should be perfect, and even more low end coupled with the 18" tires
i say you have other problems ?
hows the carb?? good and clean ?,
filter clean ?
airscrew adjustment ?
what fuel/oil mix you running ?
how's the compression ?
or maybe your just expecting more than a blaster can provide ?
Click to expand...
i forgot to mention that, good catch, yes, its 14/40. all the things you mentioned are good, comp 145, the guy i got it from did a piston a few months ago. carb was rebuilt when i jetted. only run golden spectro mix 32:1. it rips pretty good it just take a min of uuugh to get there. i was asking if there was a good combo that worked well through out the power range to help the fmf's shortcomings? ive tried the 13/40 and i did feel less bog. youre saying the 13/40 combo works best?
 
thats what I, and most trail riders use
open area riders like the 14/40, i hated it, and some even go as far as 15/38 or so for more top end
you could try a 12 tooth front for even more low end grunt for under $15

1 tooth up or down in the front is like 3(i believe) in the rear
 
A stock motor with a FMF can be woken up some in the low/mid region with a +4 timing mod, dual stage reeds and a reed spacer block.

You can put a 12 tooth sprocket on the front or increase the rear by 3 for some really good low power, but you will loose heaps of speed.

Warning, if you do swap sprockets always swap the full set, sprockets and chain. Old chains on new sprockets are a disaster, and vice versa.
 
awk08 said:
thats what I, and most trail riders use
open area riders like the 14/40, i hated it, and some even go as far as 15/38 or so for more top end
you could try a 12 tooth front for even more low end grunt for under $15

1 tooth up or down in the front is like 3(i believe) in the rear
Click to expand...

thats what im talikng about, the gearing/sprocket size on quads is still pretty new to me. like you said, one tooth in the front is like three in the rear. so, theoretically i could keep the 14 front and go 38 in the rear? same results? its hard to describe...uuuggghh.
 
mjgnslngr said:
thats what im talikng about, the gearing/sprocket size on quads is still pretty new to me. like you said, one tooth in the front is like three in the rear. so, theoretically i could keep the 14 front and go 38 in the rear? same results? its hard to describe...uuuggghh.
Click to expand...

The bigger the rear the lower gear!:)

Wont get much bottom with a 14.38.
 
a smaller front, or larger rear is what you're looking for, and you can't go much bigger in the rear. i may have seen a 42 mentioned before ???
go 13 or 12 in front, stick with the 40 rear
 
mjgnslngr said:
its what combo works best for the gear ratios in the trans right? would shortening the rear make for more torque, i guess is what im getting at?
Click to expand...

Smaller front, bigger rear = power.

Larger front, smaller rear = speed.

Mixing stretched chains, with new sprockets = $$$$$$$$ And vice versa!
 
Blaaster said:
The bigger the rear the lower gear!:)

Wont get much bottom with a 14.38.
Click to expand...
ok, my bad. im trying to understand it. im a car nut so ill try to explain it that way. bear with me non car guys... lets say chevy 350, 350 hydro trans. final drive on those is 1 to 1 so, if you run a set of 356 gears in the rear you get top speed but its a mutt at the jump.. 411s and its pulls like a mule but not much top end.iim trying to relate that concept to the blastys gearing. trying to figure that sweet spot of engines peak output to a rear sprocket to produce the torque. does any of that make sense?
 
we used the fmf and as the others have said u should have alot of bottom and mid thats why we used it over alot of other pipes we tried. We used a 13 if u go lower u will be shifting non stop. I agree with AWK u have another problem. probably on the pilot or needle. And as blaaster said the +4 timing mod helps.
 
Kgibson said:
we used the fmf and as the others have said u should have alot of bottom and mid thats why we used it over alot of other pipes we tried. We used a 13 if u go lower u will be shifting non stop. I agree with AWK u have another problem. probably on the pilot or needle. And as blaaster said the +4 timing mod helps.
Click to expand...
ok, i think im beginning to get it, swap back to the 13/40. best torque with the fmf. im trying to figure this out, im ordering new chain n sprockets and i wanted to make sure i get the right set up.
 
Blaaster said:
A stock motor with a FMF can be woken up some in the low/mid region with a +4 timing mod, dual stage reeds and a reed spacer block.

You can put a 12 tooth sprocket on the front or increase the rear by 3 for some really good low power, but you will loose heaps of speed.

Warning, if you do swap sprockets always swap the full set, sprockets and chain. Old chains on new sprockets are a disaster, and vice versa.
Click to expand...
i dont know if i put too much faith in the spacer, isnt that a gimmick?. whats +4 timing mod?
 
awk08 said:
spacers are not gimmicks, they don't add power but can move your powerband up or down, depending on if it is used before or after the reed cage, but cannot be run behind a v-force reeds

heres the +4 timing mod..............
http://www.blasterforum.com/do-yourself-20/diy-4-degree-timing-advance-pics-2417/
Click to expand...

Dual reeds, reed spacer between them and the jug, and +4 timing, seems to give good power down low with crisp throttle response.

I did find though, I needed to up the main jet one size.

If you are going to mess with stuff in the intake, do a plug chop to make sure it is not running lean.
 
Blaaster said:
Dual reeds, reed spacer between them and the jug, and +4 timing, seems to give good power down low with crisp throttle response.

I did find though, I needed to up the main jet one size.

If you are going to mess with stuff in the intake, do a plug chop to make sure it is not running lean.


im using a set of power reeds.i did my first plug chop after we rebuilt the carb and jetted. being in the Green Mountains it tends to run a little leaner than some. i have to say the throttle response is great. at first i left of the reed stops then i read up on awks post and put them back on. better to be safe than sorry. this is my first 2 stroke quad. had a few 2 wheelers. suzuki mostly. i gotta say for only being a 200 it whips pretty good. its sitting in the garage right now in pieces while my boy n i are doing the restore over the winter. got painting done last week. looks awesome, it came out weird but, awesome. still looking for a rear brake set up and front tires.
Click to expand...
 
mjgnslngr said:
so, cylinder-spacer-reed cage,boot, low end? cylinder,reed cage spacer,boot, top end? :-/
Click to expand...

Only delete the +4 deg timing mod for top end.

The difference is not surprizing but is noticable on the bottom side, I have not used a block to lift top end performance, so I am unable to comment.
 
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