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I am preparing to have my DRZ400 engine rebuilt. To conserve the effort I am planning to purchase a top end kit (435 big bore cylinder and piston), and lower end rebuild kit (New crankshaft, connecting rod, and all bearings/seals). If I was only rebuilding to top end I would do this myself. The lower end involves splitting the case so I don't want to tackle this on my own. A new cam chain and oil pump are also on the replacement list.
I live in Manhattan so I hope to find someone or business a little closer with the experience to handle to case split. Hopefully using the kits makes the job easier.

I've heard good things from different people about the guy who owns Extreme Cycle in Topeka. I've heard good things about the Athena 440 kit as well. If I were to have someone tear into the DRZ engine I'd really look into the WR gear kit.

Looking to do this on a budget. I am looking to restore reliability and a slight bit more power without ending up with a bike that develops other problems due to mods. If I was rebuilding a newer DRZ into a dream bike and money was no object, I might consider extravagant mods.
There are many big bore kits out there with a wide range in prices. A big bore kit with reliable components (JE piston, bored OEM cylinder) is $450. Anything beyond this is the price you pay for the expensive sticker to put on your fender to advertise their over-priced product.

The WR gear set is a definite Grab-your-ankles and wait for it expensive. For $620 it is still not a direct replacement process. You have to modify two shifting forks and grind the case. For that price I would expect they could figure out how to make it a direct drop in product.

I have heard good things about Extreme cycle. I would tackle this myself if I had a press,case puller, crankshaft puller, etc.

Agreed. I would go for reliability over power as well. I never looked into prices of any of the larger bores, but I do recall people having good results and still reliable with the Athena.

Extreme Cycle is closed. He finally had to get a real job. I wish I knew of someone too, but Extreme was the last independent I knew of. There's that guy............. that sells GasGas bikes, but I can't remember the name of his shop for the life of me. South of Topeka some where.

Found it. Santa Fe Trail Cycle in Carbondale

Paul Pasqualle, as I remember. He is the Gas-Gas dealer in Carbondale. He knows what he is doing. You might also consider Eric Green at Cycle Zone in Topeka. Eric is really good and can handle whatever you throw at him.

Stu

CycleZone was my next option. Since I have two crap engines now, I think I will partially dissasemble my original engine to inspect the connecting rod for wear. My "new" engine has a good head, so that resolves the warped head issue. I new big bore kit might get me by for awhile. The 435cc big bore kits only require REDUCING the main jet to accomodate the added CCs. (Yep, the added air volume requires a smaller main jet to account for the extra fuel it pulls).
I might get adventurous and split the case on the original engine if the connecting rod is iffy...just for the practice.

On a bike a couple years old with no major issues, a big bore kit and wide ratio gears would build a very nice DRZ. With stock gearing and standard bore, the W.R. gearing makes the performance weak at the top end. From what the specs were showing, the shift point from 4th to 5th gear could comfortably be 80 mph! Add a big bore kit and "E model 14/47 sprockets, and you have a bike geared well for trails, and still better than a stock "S" model at highway speeds. The company now offers the service for $19 to mod your existing shifting forks in jigs. The case grind is small and can be accomplished with a dremel. Still just over $700 just for the gearing mods.
http://www.advancedclutch.com/motorcycle-gears

If anyone has feedback on a case split, LMK. A standard gear puller will split the case, but the manual references a crankshaft puller to pull the crankshaft back through the case?

MacWildcat wrote: Since I have two crap engines now

OH NO! I was hoping you were just in the mood to build a hot rod out of your old engine.

Had a noticeable knock before we went to Arkansas. By the time we got done, the knock was ugly. When I drained the oil there was brass flicks.
I am guessing brass = connecting rod bearing.

I'm pretty sure the big end bearing is a steel roller bearing. Might not be a death noise. Primary gears have been know to come loose and make noise. A bushing on something like the counter balancer. I'd get on thumpertalk and get some advice before going too deep into it.

First thing I checked was the primary gear nut...tight. I thought the brass was a little puzzling too.

Inquired on Thumpertalk....brass non-magnetic flakes usually indicate connect rod bearings. Took the engine apart today, sure enough, both ends of connecting rod have play.

Checked on a crankshaft puller. A typical tool used for vertically split engines. Rocky Mtn. ATV sells a Tusk brand crankshaft puller for $59. Supposedly you can freeze the crankshaft and heat the case to slide them back together. The puller is a more refined method of assembly.

I worked in a hermetics repair shop one summer in my youth. Parts that I used massive tons of press to disassemble they would reassemble by hand. The method .....freeze the shaft and put the rotor in the oven and heat to 300 degrees. 'They slid together effortlessly.

bird man wrote:I worked in a hermetics repair shop one summer in my youth. Parts that I used massive tons of press to disassemble they would reassemble by hand. The method .....freeze the shaft and put the rotor in the oven and heat to 300 degrees. 'They slid together effortlessly.

One inch of steel will expand 0.00000645 inches for every degree Fahrenheit increase in temperature

http://mathcentral.uregina.ca/QQ/databa ... /jim2.html

Five ball sixty four is the mnemonic device used to remember. I'm lucky with totes of pelletized dry ice available to me (−109.3 °F) then heat my part to 230-250, some splines I'll heat to over 300, kevlar gloves for sure!

Yep, the freeze/heat process works for some of the process, installing the crank in one side of the case. The final case assembly requires a puller.

Bought all three tools required for a DRZ400 case split. Might have go into the tool rental business.

Might be too late, might not be feasible ... Acetone (available in paint / solvent section of hardware store) has a freezing point below that of carbon dioxide (dry ice). Thus you can put dry ice in liquid acetone and the acetone will cool to the melting point (sublimation point) of CO2. -108oF vs ~0oF for a freezer.

Why do this? If the part to be cooled can be immersed in a container and not too much is required, the liquid will allow a faster (and probably better) transfer of heat out of the part. You don't have to hold the dry ice against the part.

As classroom demos I have frozen flowers in the above mixture and had them shatter against the white board. (Chalk boards are soooooo old school ... :-p )

I acetone thing very interesting, and will remember that trick when I have to replace the bearings in my vintage bikes. It would work well to replace cast iron cylinder sleeves too. Thanks!

Not sure I need to get a bearing that cold to install it. I would be a little concerned about damaging internal parts. I know with wheel bearings, the freezer for the bearings, and a heat gun for the hub is plenty.

The rebuild kits are supposed to show up tomorrow so I hope to start putting it back together this weekend. Getting the main bearings out without the aid of freezing will be the test on how tight they fit. I will have to rely on the heat gun to heat up the case.

All told, the price for a DRZ400 motor rebuild from a repair shop would have cost $2,000. Hoping to get through this on my own for about $1,000. Found a good mechanic that specializes in the DRZ400 rebuilds. Supposedly the DRZ435 big bore actually reduces some stress on the motor by providing more HP without as much rpm revs.

Well I finally got the project completed. I now have a KLX 435!

A full lower end case split and rebuild is dooable by anyone with competent mechanic skills and a good manual. I bought a lower end rebuild kit that included the crankshaft/connecting rod, main bearings, and all the seals. I installed a big bore kit...much easier than attempting to hone and mic out a cylinder and replacement ring set.

Sweet! Congrats! I was wondering just this weekend how it was coming along.
LMK if you'd like to go for a ride sometime.