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DRZ400 bottom end rebuild difficulty?

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Ok so assume I know how to work on cars, head gaskets, etc. and have done a few top ends, one on a DRZ. Assume I want to buy a stroker lower end rebuild kit and Wiseco piston with rings.

 

Now I know the case needs to be split. How complicated is it past that? How much stuff has to be removed?

 

Another question.... how easy is it to press in and out the cracnkshaft and crank bearings? Is there a workaround for the specialty tools (besides case splitter) or am I going to need to take it to a shop?

 

I HATE having others work on my cars/bikes.... bad experiences before I learned to do it myself. I'd like to tackle this myself.

 

Thanks in advance, and any advice would be greatly welcomed.

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Difficulty is hard to assign,,,, as difficult to one is impossible to another, or comically simple to a third. 

 

That said....... it is a doable job to a reasonable experienced wrench who takes their time, uses all the resources available, has the proper tools, understands when they don't understand and has the discipline to STOP until they do.

 

Case splitter and crank puller are IMHO required special tools, as will be the flywheel puller.

Someone will come along and say BS, you only need a claw hammer, three jaw puller and long flat blade screwdriver...if you choose to go that way... best of luck... I know a guy that hit the ground as his parachute deployed.. He lived.. Me I still prefer to deploy mine a few feet AGL. Same with taking short cuts and using the wrong tools to do a job...

 

A digital camera is a GREAT tool to have as well.. the camera and Zip lock bags with a sharpie will assist greatly on the re assembly. 

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Ok so what I'm curious about is what has to be removed after the cases are split in order to pull the crank and crank bearings out and install new ones?

 

Also, the crank bearings... are they only possible to get out with specialty motorcycle bearing tools, or would an automotive one work? I can rent one free from autozone if there isn't a big difference. Otherwise I have to pay a shop to do it and I don't trust them.

Edited by Dirtsketcher
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Ok so what I'm curious about is what has to be removed after the cases are split in order to pull the crank and crank bearings out and install new ones?

What has to be removed?  .. Well everything so it can be cleaned and inspected..

 Once the case is split.. the transmission and crank are really all that is left in the case that "comes out"

 

The main crank bearings will likely stay in the case,,, but occasionally come with the crank.

If your taking the time and hassle of splitting the case, install a new crank and main bearings... Dont mess with high hour or mileage, unknown previous owner used cranks.

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I would need motorcycle-only specialty tools to do this.... to pull the crank out and reinstall.... and also to replace the bearings? A shop quoted me $130 if I brought all the parts and had the case ready to separate. Id rather do it myself, but not if I have to buy $300 in tools.

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Best thing to do if you're to split the cases and have never done it before is to 1. get a good service manual, 2. (as previously stated) Take pics with digital camera, 3. take a piece of cardboard and when you split the case/take apart something complicated draw the shape on the cardboard with sharpie and put the bolts in there respective place. (first time I split a case on my rm125 this helped alot during re-assembly as the bolts varied slightly in length). 4. get a paint marker and a good magnet tray and just take down simple notes with parts that will help make it a breeze to re-assemble. Just habits I have to make things easier for myself if I am totally new to a machine.

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I would need motorcycle-only specialty tools to do this.... to pull the crank out and reinstall.... and also to replace the bearings? A shop quoted me $130 if I brought all the parts and had the case ready to separate. Id rather do it myself, but not if I have to buy $300 in tools.

Not $300

 

 But not free..

Motion Pro Flywheel puller $40

http://www.rockymountainatvmc.com/p/49/-/182/755/93/17155/Motion-Pro-Flywheel-Puller

 

Tusk Case splitter  $40

http://www.rockymountainatvmc.com/p/43/-/171/989/-/17167/Tusk-Crankcase-Splitter-Separator?term=crankcase%20separator

 

Tusk Crank puller $60

http://www.rockymountainatvmc.com/p/49/-/182/755/-/17166/Tusk-Crank-Puller-Installer-Tool

 

 the case splitter and crank puller can be home built if your a metal fabricator, can weld, machine, ect.

 

The flywheel puller can be home built if you are an accomplished machinist.. but at the buy in of $40... it's not worth my time and materials to make one... 

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Not $300

 

 But not free..

Motion Pro Flywheel puller $40

http://www.rockymountainatvmc.com/p/49/-/182/755/93/17155/Motion-Pro-Flywheel-Puller

 

Tusk Case splitter  $40

http://www.rockymountainatvmc.com/p/43/-/171/989/-/17167/Tusk-Crankcase-Splitter-Separator?term=crankcase%20separator

 

Tusk Crank puller $60

http://www.rockymountainatvmc.com/p/49/-/182/755/-/17166/Tusk-Crank-Puller-Installer-Tool

 

 the case splitter and crank puller can be home built if your a metal fabricator, can weld, machine, ect.

 

The flywheel puller can be home built if you are an accomplished machinist.. but at the buy in of $40... it's not worth my time and materials to make one... 

 

Thanks a lot for the links and taking the time to do that. I will probably go that route then, since it is about what's quoted for me for labor for the shop to do it, and I will own the tools and do my own good work. What about the crank bearings?

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Thanks a lot for the links and taking the time to do that. I will probably go that route then, since it is about what's quoted for me for labor for the shop to do it, and I will own the tools and do my own good work. What about the crank bearings?

The crank bearings most often stay in the case as the case is split.. Once the crank is out of both sides of the case, the mains are driven out of the case.

 

To re install, most will heat the case and freeze the bearings and they will all but drop in to the cases. (there is a train of thought that doing this will allow moisture to condense on the bearing race and cone surface.. and as we have seen many cases of even light water intrusion to the engine or oil, left for a few days.. cause enough damage to later lead to crank / rod failure.. I have stopped this procedure unless I plan on having oil in the motor and it running that same day I don't build enough motors to know for sure if it's an issue or not...I know what has worked for me, what I've seen from others, and personally decided the extra ease of freezing/ heating bearings and case was not worth the later hassle and questions asked if it fails.) .)

 

The crank is pulled into case using the crank puller. Other side case reassembled and dropped into place. Using the case screws to reassemble the cases... and that works most times. If after reassembly you have some rotational resistance, use a soft head mallet to moderately tap the three shafts coming out the right side case once each and check rotation again.. if you can not clear up the binding in one or two taps, check for another reason. 

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This is good stuff! I feel the same way as the OP on this. I don't let anyone touch my stuff for the same reasons. I was an ASE auto tech before my stint in the US Navy as a Machinist Mate so I'm pretty handy but I have never split a case on a motorcycle nor do I own a shop manual. After reading this I am confident that with a manual I would have no issues performing a full stroker overhaul on my DRZ. Thanks to the OP for asking and E Marquez for the Insight links!

Edited by Dr. D

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If/when I go larger, I'll have Eddie Sisneros do the work. I can do it but he can do it much faster. I'm slow 'n lazy. :D

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Thanks for all the info..... I went the sellout route and bought a complete bottom end off eBay with 5K miles, $489 shipped. I know I'm rolling the dice but I'm desperate to get riding, and I can work on rebuilding my original engine over the winter.

 

NOW, for the next question lol.... which piston should I go for? I have heard forged is better than cast, but I am looking at this $85 Namura " high silicone content for added strength". Should I just spring the extra $40 for a forged Wiseco? For the record, my top end was fine, no real oil burning, no smoking, no scoring on walls.... so I'm looking for the regular 90mm size right?

 

I also am picking up a full engine gasket set for $65 from Winderosa, which is a good brand right?

 

Lastly, my piston and head have thick deposits (probably from Citgo gas her whole life)... so to clean the combustion chamber portion of the head and valves, can I use a wire brush or is there a better chemical method?

Edited by Dirtsketcher

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Cleaned and prepped for the bottom end switch, engine is out.

 

Noticed cylinder jug has light scoring on the forward part of the cylinder, needs to be honed. I saw a Namura overbore piston (.020 more) so its 90.50mm. Should this be used of your bike had 17K miles and a honed cylinder sleeve?

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Cleaned and prepped for the bottom end switch, engine is out.

 

Noticed cylinder jug has light scoring on the forward part of the cylinder, needs to be honed. I saw a Namura overbore piston (.020 more) so its 90.50mm. Should this be used of your bike had 17K miles and a honed cylinder sleeve?

By the time you pay for a quality shop to overbore , then plate the cylinder($200 or more)  for the piston and rings ($150 or so) you choose... you might as well get a cylinderworks BB kit (which includes a Cometic top end gasket kit) and be done with it. 

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Not meaning to have a shop overbore it.... just does the wear from the mileage and the honing involved for the cylinder..... will .020 increase the service life of a slightly worn top end?

 

Reading about forged vs cast...... Is the Namura with increased silicone content going to be sufficient?? I do a lot of wheelies.... I dont know if that matters to the piston..... from what I gether a forged piston can take more abuse?

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Not meaning to have a shop overbore it.... just does the wear from the mileage and the honing involved for the cylinder..... will .020 increase the service life of a slightly worn top end?

It's not a 1970's two stroke... you cant just install a "next oversize" piston in it.

 

The nikasil plated bore in that OEM cylinder is harder then the aluminum piston. 

If you really want to reuse the cylinder, it should be cleaned up and have a ball hone run though it.... The ball hone will not "hone" a nikasil plated cylinder.. that takes a rigid diamond hone.  BUT the ball hone will clean up stuff deposited on he cylinder walls (so will muratic acid, but it's nasty to work with)

Then once clean, use (take it to a machine shop or good bike shop) a cylinder dial indicator to measure the bore. 

 

 Namura has a following on both sides..

Some claim they work great, never fail and will run 10,000 hours, some claim they fall apart in 2 rides....The truth is likely between the two extremist views.

 

I've installed a few when they came with BB kits I was provided by the rider... No issues I know of, but those are not bikes I see again.

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Ok so I just ordered a Wiseco 90mm with rings, and I bought an Athena full engine gasket kit ($108 geeze).

 

Since my cylinder bore has up/down scratches on the front side.... and nowhere else, was this maybe caused by piston slap??

 

Could that have been the source of my knocking?? The grooves are perceptible by rubbing a finger across them.... luckily I have my bosses old one from when I did his big bore.

 

What I'm asking pretty much is if this COULD be a symptom of a bad big end, too many wheelies, or some other problem? Again, the piston and bottom of the valves has a ton of deposits... blow by perhaps?

 

What is the usual cause of vertical scratches on the forward side of the cylinder bore?

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So many impossible questions to answer.

 

 

Since my cylinder bore has up/down scratches on the front side.... and nowhere else, was this maybe caused by piston slap??------Yes, maybe.

Could that have been the source of my knocking??-----Yes, maybe

The grooves are perceptible by rubbing a finger across them.... luckily I have my bosses old one from when I did his big bore.------So you are not going to use the cylinder with the scratches in the bore, right?

What I'm asking pretty much is if this COULD be a symptom of a bad big end,------Yes. a loose big end bearing can throw metal up on the bore and cause scratches.

too many wheelies,--------?? how would I know

or some other problem?------- Other problems are always a possibility

Again, the piston and bottom of the valves has a ton of deposits... blow by perhaps?-------Heavy combustion chamber deposits indicate oil consumption.  Ring seal, valve stem seals, and crankcase vent system can all cause that

What is the usual cause of vertical scratches on the forward side of the cylinder bore?------I would need to see the piston, bore and the lower end to offer a reliable guess.

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Edited by Noble
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