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Engine Builder for Dirt Bike needed

Jeff a BARFER does great work and specializes in dirt/dual sport bikes.

Morris Industries
16400 Lark Ave
Los Gatos, CA 95032
Phone number (408) 921-7846
 
i had blonix do and over bore, port/polish, and rifle my carb on my cr back in the day and he did a great job. not sure if he is still around but worth checking into.
 
I used SIXFIVE0 and was very satisfied with the work, if you are looking for a place that knows dirtbikes in the area I can assure you they do. Hope it helps and glad to see someone that doesn't just get a new bike ! Good luck
 
OP - I have a plated dirt model DR350, too. A few things...

The 385cc rebuild has some positives and negatives. Honing the stock cylinder out for the 385 ends up with relatively thin cylinder walls, some of which have cracked on people. There IS a better solution. The top end of the Suzuki Eiger ATV is VERY similar to the DR350, and a lot of those parts CAN be bolted up to the DR350. The Eiger was bored a little bigger though (~376cc I think?), though, and Suzuki has a thicker piston sleeve from the factory... so you can actually use the Eiger cylinder in combination with the 385cc piston the DR350. Bolts right up, and gives you significantly thicker cylinder walls post boring.

Second.. the 385cc piston results in higher compression - 10.5:1, if I recall, as compared to the stock 9.5:1. Some users have experienced detonation. I actually have a rather rare Cycle Gear 400cc piston new in the box for the DR350 that I've been sitting on for about six months now, along with an Eiger cylinder. It's also 10.5:1. I'm still on the fence whether or not I want to install it on my bike.

That's a choice you'll have to make for yourself. 10.5:1 is fairly high compression on an air cooled bike that doesn't have an oil cooler. Storing the oil in the frame probably helps to cool it off a little more, but even so...

Another thing... The head on the DR350 is infamous for failure, because of folks' inability to correctly check the oil level. As a result, the supply of heads has diminished. Good news? Turns out you can ALSO use a head from a Suzuki Eiger / King Quad. Suzuki STILL makes that head, to this day. You have to drill out a hole on top in order to install a bung for the oil return, but that's trivial. Finding a gently used head from the Eiger ATV is a lot easier (and cheaper) than getting one from a DR350. In many cases, it can be cheaper to do that than to have the DR350 head rebuilt / cut etc. A lot is the same - valves etc. I want to say you lose the manual decompression, but since the cam has auto decompression, it's really not a deal breaker.

For what it is worth, the rebuild really isn't all that hard, if you have a little mechanical ability. I'd also recommend replacing the cam chain while you're in there.
 
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>I have heard good things about engine Dynamics and think Steve has mentioned using them for this work (very nice work btw) on his XRL builds. I don't know if Steve will work on DR's but if he will, you should take him up on it.
 
Jesse Kientech in Grants Pass. Semi retired but still working. That guy has probably forgotten more about the DR350 than most folks will ever learn. Pioneer of many mods for them. I have a '98 DR350s with one of his 440cc kits that thing rips. Super nice guy totally old school square dealer.
http://www.kientech.com/
 
Kestrel said:
OP - I have a plated dirt model DR350, too. A few things...
Click to expand...

Hey Kestrel...I've seen your posts around over the years regarding the DR350. Thanks for the info. I've created a Build Thread at ADVrider for this project that you can check out and see my specific plans and progress.

For the motor build, in short:
-- I've sourced an Eiger cylinder and 83mm piston locally and will be picking it up by next week.
-- I've spoken with Steve, the XR builder, and he's down to do the build/assembly if I get him all the parts. (Perhaps I could manage assembly on my own but I know the motor will be down for way too long if I do, and I just want the confidence of having my engine put together by someone who's put together a hundred engines.)
-- I've gotten pricing from EDCo, who will be handling the machine work.

The only thing I'm still trying to decide (and the thing that will take the build costs from totally reasonable to a little painful) is how crazy to get with the head. Cam-ing it will mean stiffer valve spring kit, hardened rocker arms, and might as well have EDCo do their competition valve job at that point to get the most out of everything.

Kestrel said:
...10.5:1 is fairly high compression on an air cooled bike that doesn't have an oil cooler.
Click to expand...
This is disconcerting. I wouldn't normally consider 10.5:1 too high for 91 octane, but I have been looking into the possibility of adding an oil cooler anyway. I'll be bringing this up in the build thread.

So I'll eventually post back my experiences with the various folks involved with this motor build for posterity, but if anyone has more info or questions about this project in general, swing by my build thread so I can keep things organized! I'll also soon have a thread in the AFM section with race-specific questions and info.

Thanks everyone for your recommendations!
 
JimE said:
Jesse Kientech in Grants Pass. Semi retired but still working. That guy has probably forgotten more about the DR350 than most folks will ever learn. Pioneer of many mods for them. I have a '98 DR350s with one of his 440cc kits that thing rips. Super nice guy totally old school square dealer.
http://www.kientech.com/
Click to expand...

Yeah, Jesse helped me with parts and advice to get my carb set up properly back when I first got the bike, but hasn't exactly been reachable recently.
 
10.5:1 isn't very high on a watercooled motorcycle engine. It's fairly high for an aircooled motorcycle engine, as the head runs at a much higher temperature.
 
The Villain said:
This is disconcerting. I wouldn't normally consider 10.5:1
too high for 91 octane ...
Click to expand...

... thanks for your build thread link! :thumbup

had fun years ago actually cc'ing the combustion
chamber on a head using fluid and a graduated cylinder and
doing the math to figure out compression ratios that
various head/base gasket thicknesses would provide
on a particular engine (used a book called The Auto Math Handbook) ...

neat to figure out the stock-piston CR vs
the overbore piston CR ... what I recall is that most
of my performance gains were not from simply having more cc's
but rather came from the overbore's increase in compression ratio ... :dunno

the street/dual sport top ends I do now, I build up
strictly for stock/low compression ... for bad Baja gas and
street engine longevity ... my bikes are notoriously boring
to ride ... :laughing

... here is a link to an ADV post that
quotes a combustion chamber volume
for a DR350 as 40 cc's ...

... be fun to hear what compression ratio
you decide on for your build ... :party
 
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The Villain said:
This is disconcerting. I wouldn't normally consider 10.5:1 too high for 91 octane, but I have been looking into the possibility of adding an oil cooler anyway. I'll be bringing this up in the build thread.
Click to expand...
The engine that Steve built for me has a 10.5:1 piston in it and the displacement has been increased from 644 to 675. I've only run 87 octane in it and have never had issues with pinging or detonation. The only big difference other than significantly more power is that the starter motor has a tougher time getting past the first compression stroke than before the rebuild. Rebuilding the starter and a new battery have mostly made that a non-issue.

I haven't found the need for an oil cooler so far. I don't usually ride much when it's over 85 degrees or so, and have seen no hints of overheating. I run it a little on the rich side to help things out though. It's been this way since April of 2015.

I don't know if the Honda engine has a better combustion chamber than the Suzuki, but 10.5:1 doesn't seem to be high enough compression in that engine to need higher octane fuel.
 
One more vote for engines only... they rebuild my cr80 motor for about $900... a few years back.
 
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