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Big Bore Kits On Dr-Z400sm?

Idioteque

Idioteque

_________________________
Joined
Oct 20, 2009
Location
Martinez
Moto(s)
FZ9
Name
Steven
Hey, i've heard talk about these, but never heard if there were any downfalls to bore-ing out.

Is it safe?
Any long term damage possible?
How much is it? (I realize different kits have different price, but an est.?)
Any details you guys have, please let me know.
 
Some folks get cranky with second/third hand information, but I have one buddy who's into the drz's with his little crew. The consensus is that the Athena 440 kits are dead reliable. Also, I'm told you also need exhaust and to ditch the butterfly carb to make the most of it. I believe the Athena kits are ~600, and I've heard great things about the JE kits for other bikes, they run ~400.
 
Idioteque said:
Hey, i've heard talk about these, but never heard if there were any downfalls to bore-ing out.

Is it safe?
Any long term damage possible?
How much is it? (I realize different kits have different price, but an est.?)
Any details you guys have, please let me know.
Click to expand...

It is very unsafe.. you'll probably get hella speeding tickets and reckless driving tickets now.

Seriously.. unless you jet it wrong or install the piston backwards or jazz up the cam timing, it'll work just fine.
 
Sweeeet, ill give the athena one a looksies. Still up for more peoples' input too :)
 
I had a Big Jugs 450 kit on one of my DRZs, along with cams, FCR carb, full yosh, etc..

It was pretty damn quick, but sucked gas like coca cola. A quick snap of the throttle and the front will come up in 3rd gear. If you get it properly done, the kit should last a while. Just don't go riding freeway everyday.

Never got to dyno it, but I estimate it to be close to 45-50hp.
 
Cant speak for the DRZ but the athena kit is probably the most well known on thumpertalk in the Yamaha section. The cylinder is supposed to be as good as stock with nikasil coating and larger cooling ports. Tons of ppl running em.
 
I am in the middle of a BB kit / cam upgrade right now on my 09.
Bike is right at 2K miles. I got my BB kit through Big Bore Thumpers down south.Even came with a manual cam chain tensioner.
They list the kit as coming with a CP piston , but mine has a JE instead.
$430 and it was here in 5 days ( ordered on a friday afternoon . They had to wait till monday to order the piston.)
I think the only time you get in trouble with BB kits is putting them on an old bottom end.And I'm thinking they are every bit as reliable as a stock bore motor. Guess I'll be finding out.
Install can be done in a day easy. I'm dragging due to a cold. Started at noon and just got done torqueing(?) head and setting cam timing 7:30 ish.
 
Idioteque said:
Mine gets about 60-70 mpg right now, what did yours get modded?
Click to expand...
You mean mpg or miles per tank? Thats some out standing mileage for your DRZ. I only managed 55mpg with the stock engine. Got slightly less once I jetted and air boxed.
I never understood why one would do the big bore and fcr mod. The DRZ is what it is. I had this uncertain feeling the bore kit would eventually sacrifice the rod bearings because of the load. Just me I guess.
 
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nine_inch_rear said:
You mean mpg or miles per tank? Thats some out standing mileage for your DRZ. I only managed 55mph with the stock engine. Got slightly less once I jetted and air boxed.
I never understood why one would do the big bore and fcr mod. The DRZ is what it is. I had this uncertain feeling the bore kit would eventually sacrifice the rod bearings because of the load. Just me I guess.
Click to expand...

I would agree that there is probably slightly more load placed on the rod bearings with a big bore , but these engines appear to be overbuilt and I don't think it is of any concern.

I'm doing the BB / cams because I want to change the power characteristics of the engine. I want a little more mid range upper end for wheelies.
 
dbatman said:
Jetted with pipe and 3x3 I would get 60MPG.
Click to expand...

right, but have you seen my list of mods? Also forgot to mention that I had a thinner base gasket, and one of those power now carb plates.
 
stan23 said:
right, but have you seen my list of mods? Also forgot to mention that I had a thinner base gasket, and one of those power now carb plates.
Click to expand...

Your a carb and carb plate ahead of me. I'm still with the mikuni. We'll see what kind of milage I get with the 434 kit and cams.
 
It won't be too bad w/o the carb.

I also had a R6 throttle tube to tame the wild beast! haha
 
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