Will a Big Bore really get me what I am looking for?

[screechingdemon]

I spend the weekends riding offroad in woods/trail type riding and put the SM wheels on the bike for the commute to work during the week. Overall I like how the bike runs since I installed the FCR 39, especially the torque on the bottom end up to about 7K RPM. It runs good up to about 70-75 mph, but doesn't quite have enough on top end to be able to pass other traffic and make a statement. It passes fine, but at interstate speeds it would sure be nice if there was just a little bit more there. Would a big bore kit give me the extra power I am looking for? I really enjoy the size and handling of the bike both on and off road. I am not looking at doing anything radical but was thinking a big bore such as a 440 kit might do the trick. Would this require a different exhaust, different cams or any other mods along with it. Do you have any other recommendations on set ups to look into?

Current setup 2001 S/SM model with the following mods:

FCR 39, EMP needle

3X3

KN filter

Complete "E" Exhaust (I like the stealth mode)

2002 RM forks and tree

elevation 1300'

15/41 gearing SM wheels 15/44 dirt wheels

Thanks,

screech

[Wayward Son]

good bang for the buck.you can just bolt one on.

[Jim Hale]

It passes fine, but at interstate speeds it would sure be nice if there was just a little bit more there. Would a big bore kit give me the extra power I am looking for?

The drz will always be underpowered for the highway, doesn't matter if you go big bore or not. Big bore definitely gives you more power, but if you're thinking you'll have a decent highway bike... you won't. It's just not a highway bike, particularly in windy Kansas.

[hi_im_sean]

theres no relpacement for displacement

[Jim Hale]

theres no relpacement for displacement

Nor for weight. It's really both. A zx10 (435 lbs FI) would smoke my zrx1200 (485 lbs 4-carbs) due to it's lighter, more modern engine and better aerodynamics. That being said, a heavy bike is way more comfortable on the highway and less susceptible to wind.

Certainly all things being equal though, displacement wins.

[shortburb]

play with gearing? maybe a +1 front? ...to keep you a little lower in the rev range but have the extra 1 or 2 mph top end?

[bill1960]

good bang for the buck.you can just bolt one on

Eddie, are you referring to the MT kit, and, using screechingdemon's bike as an example, roughly what HP gains could he expect .

[Wayward Son]

i use the mt kit pretty much exclusively.

4hp peak with greater gains before and after peak.

[bill1960]

use the mt kit pretty much exclusively.

4hp peak with greater gains before and after peak.

thats pretty good, ~$100 per hp

I suppose the "just bolt on" idea is OK if the bike is low milage

My bike has done 25000km and still going well but I'm wondering if conrod bearings and valves should be replaced at same time?

perhaps best to wait until a major rebuild is required ?

[hi_im_sean]

Nor for weight. It's really both. A zx1000 (435 lbs FI) would smoke my zrx1200 (485 lbs 4-carbs) due to it's lighter, more modern engine and better aerodynamics. That being said, a heavy bike is way more comfortable on the highway and less susceptible to wind.

Certainly all things being equal though, displacement wins.

ummmmm... it was implied that everything else remains constant... duh:bonk:

[iowaBClivewire]

you may like what 16-41 gearing with the different/better torck curve of "E" cams will get you with your stock bore

but if it was me aney time that head comes off I would replace those 2 peace valves with good SS ones

[Wayward Son]

thats pretty good, ~$100 per hp

I suppose the "just bolt on" idea is OK if the bike is low milage

My bike has done 25000km and still going well but I'm wondering if conrod bearings and valves should be replaced at same time?

perhaps best to wait until a major rebuild is required ?

valves at a minimum.

[MotoChris521]

good bang for the buck.you can just bolt one on.

Wouldn't cams increase top end rev ? Seems my E revs out mucho further than my S .

[Wayward Son]

depends on the cams,but yes.

he asked about the big bore only.

[pjk]

10% more cc`s = 10% more

[Wayward Son]

the big bore works really well becuase it moves the cylinder wall away from the valves effectively unshrouding them to a degree.the flow of the head goes up.

[screechingdemon]

depends on the cams,but yes.

he asked about the big bore only.

If I was to do the cams also, what would you recommend? The bike currently has about 7K miles on it. Which big bore kit would you recommend? I prefer a kit that comes with a separate cylinder so I can keep my stock one. By adding such a kit would I affect the reliability of the motor?

[screechingdemon]

play with gearing? maybe a +1 front? ...to keep you a little lower in the rev range but have the extra 1 or 2 mph top end?

I have been toying with the idea of putting a 16 on the front or putting a 38 on the rear. If I do that then I will probably have to run a separate chain for the sm and dirt wheels but I already have two available to do that. With what I have now 15/41 SM and 15/44 dirt I am able to use the same chain for both.

[Wayward Son]

If I was to do the cams also, what would you recommend? The bike currently has about 7K miles on it. Which big bore kit would you recommend? I prefer a kit that comes with a separate cylinder so I can keep my stock one. By adding such a kit would I affect the reliability of the motor?

if you want to keep your stock cylinder,athena is the way to go.

hotcams stg 2 if you can find them.hotcams had a few left.

[Erik Marquez]

If I was to do the cams also, what would you recommend? The bike currently has about 7K miles on it. Which big bore kit would you recommend? I prefer a kit that comes with a separate cylinder so I can keep my stock one. By adding such a kit would I affect the reliability of the motor?

With what you have posted.. MT with a new/used cylinder or the Athena kit. 94mm 13.5:1 CR, RHC cams or Hot cams, valves, springs, tops and locks from RHC.

IMHO I would not change cams without doing after market valves, preferably RHC's... And again IMHO,, As far as I'm concerned,, any power mod, RPM upping or using MOD requires new valves and springs. My personal experience and that of close friends plus other DRZ's I've worked on has proven to m, if the bike will be ridden moderately to hard,, not spending the extra money on Valve train now, will only end up costing you the price of a crank up rebuild.

Pay a little more now, or a lot more later.

To each his own, your mileage may vary.