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DRZ400SM Engine Full Rebuild Tips & Advice

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How's it going guys?

So recently, my DRZ started making some crazy noises / vibrations that I could feel through the clutch lever. Upon tear down, my clutch and plates looked perfect, so I dug a bit deeper and removed the side cover and clutch basket. Behind that basket, this is what I found:

 

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The bearings from the clutch shaft fell apart and needless to say, I'm going to have to split the case to replace that bearing. I'll be doing the work myself, but since it's already going to be apart I wanted to make some upgrades while I was at it.

 

I was thinking of doing the following:

 

- ACT Wide Ratio gear set since I ride lots of freeway.

- All new bearings and seals of course.

- Slipper clutch.

- New piston rings.

- New valves and springs (possibly oversized).

- Port and polish cylinder head.

 

My goal is to rebuild the motor and make it as reliable as possible, as well as add so more power to it if possible.My current setup is:

 

- Full Yoshi pipe.

- Hot Cams Stage 2.

- Cylinder Works big bore.

- FCR Carb 39mm.

- 3x3 Mod

 

Just wanted to see if you guys had any advice/tips/suggestions since my bike will already be apart. Thanks in advanced!

 

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PS: Anyone have any idea how to remove the rotor / flywheel without the special factory tool? Thanks!

 

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PS: Anyone have any idea how to remove the rotor / flywheel without the special factory tool? Thanks!

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Don't even try it. Just buy the tool, it is cheaper than a new flywheel when you ruin it and you will ruin it. Also I would skip the slipper for street only use and use the money elsewhere, that is totally up to you however. If you want one get one. ACT gears are always a good choice

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Don't even try it. Just buy the tool, it is cheaper than a new flywheel when you ruin it and you will ruin it. Also I would skip the slipper for street only use and use the money elsewhere, that is totally up to you however. If you want one get one. ACT gears are always a good choice

 

Cool. Just called my local shop to order the tool. Thanks.

Yes, ACT gears were the ones I was looking at. I've dealt with ACT in the automotive world, never had a problem with their products.

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Man, no more responses? Crazy...

Anyone ever used a lightened flywheel?

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4mm stroker crank, act gears, while its in bits critically analyse your crank for wear if you decide to keep it, some of the bits of s**t from the bearing failure may have got into the big end, my bike just did the same but it was the crank bearing, the thing also locked up, thankfully no real damage has occurred to anything else, I'm fitting the ACT gears, 4mm stroker crank and CW BB kit, the slipper clutch mod is a waste unless you racing and it can be done at any time without splitting the cases, better off spending the money on getting whats inside the cases completely sorted the way you would like it long term, crank is worth about a hp per mm of extra stroke and heaps more torque, plus leaving it at 4mm means you can use your existing cylinder kit, you may have to put in the 3 layer base gasket to reduce the comp, have a real solid look at your output shaft as well, if you go to the extent of a port and polish yes the o/s valves would be ok, but the 39mm carb will not flow enough to take advantage of it, hence the 41mm mod for stroker motors, if you leave your 39mm carb better off replacing the valves and springs with a/market stainless valves and good springs/retainers, and leave the head alone, it flows good enough stock, my 2 cents.

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Looking forward to hearing how you make out with the act gears. Hopefully going to be putting a set in my bike over the winter... Keep us updated with lots of pictures!

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I noticed one of your bolt heads was rusted, on the right case half, then i saw all the antifreeze. Where you leaking antifreeze into the cases?

I ran stock gearing I thought overall, it worked fine. Except for the 1500 mile trip florida to Texas and back, where I really need to cruise about 85 mph to be competitive, drop atooth or two on the rear. Personally Id do that before I shave down shift forks and go with aftermarket gearing, till its atleast well proven.

Edited by Spud786

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I noticed one of your bolt heads was rusted, on the right case half, then i saw all the antifreeze. Where you leaking antifreeze into the cases?

I ran stock gearing I thought overall, it worked fine. Except for the 1500 mile trip florida to Texas and back, where I really need to cruise about 85 mph to be competitive, drop atooth or two on the rear. Personally Id do that before I shave down shift forks and go with aftermarket gearing, till its atleast well proven.

The green fluid is oil, Motul 300V 15W-50. I had no antifreeze leaks.

I was running 16-38 gearing and the rpm's are to high for a long cruise down I-15.

I appreciate the advice, someone has to be the guinea pig. I should recieve my flywheel removal tool soon, so I can continue the project.

In the meantine, I'll rip around on my XR. : )

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4mm stroker crank, act gears, while its in bits critically analyse your crank for wear if you decide to keep it, some of the bits of s**t from the bearing failure may have got into the big end, my bike just did the same but it was the crank bearing, the thing also locked up, thankfully no real damage has occurred to anything else, I'm fitting the ACT gears, 4mm stroker crank and CW BB kit, the slipper clutch mod is a waste unless you racing and it can be done at any time without splitting the cases, better off spending the money on getting whats inside the cases completely sorted the way you would like it long term, crank is worth about a hp per mm of extra stroke and heaps more torque, plus leaving it at 4mm means you can use your existing cylinder kit, you may have to put in the 3 layer base gasket to reduce the comp, have a real solid look at your output shaft as well, if you go to the extent of a port and polish yes the o/s valves would be ok, but the 39mm carb will not flow enough to take advantage of it, hence the 41mm mod for stroker motors, if you leave your 39mm carb better off replacing the valves and springs with a/market stainless valves and good springs/retainers, and leave the head alone, it flows good enough stock, my 2 cents.

I'll definitely look into a 4mm stroker crank. I guess I'll have to decide whether I want to upgrade my carb or not and that will tell me what size valves to run. Thank you.

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So after a great opening season at the desert, I came back home to try out my flywheel remover tool I received the night before I left. It worked flawless, thank for the advice. Definetely wasn't getting that off any other way without damaging something.

 

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I split the cases and so far I have seen no collateral damage from the bearing failure. That's always good news. That frees up some money for other stuff.

 

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Here's some pictures of the bearing that failed.

Luckily that's all that failed.

 

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So now it's time to fix and upgrade it. I've decided what route to take.

Since funds recently got a bit tight, I have decided to just do a wide ratio gearset, new OEM size valves and springs, port and polish the head and tune the carb as best as possible. That should give me a reliable motor that will last quite awhile and still be fun.

 

So I had a question. I'm making my parts list so I can order everything in one go. I was looking at replacement bearings. Are OEM ones the only ones available for a rebuild or are there better bearings from other brands/sources?

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OEM are good, that's what I use....

Add a new piston to the list to go with the new rings in your original list....It's apart is enough reason to go with piston replacement...

Oversize valves are not needed with big bore, so good thinking to stay with std valves..

 

Port and polish the head.????..What do you plan on doing exactly to your ports and who is doing the work?....

 

Tune your carb????....Has the o ring mod been done (with wire),?? that's all it may need.....list your current settings and we will see if other messing with it is required

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Looking forward to the successful outcome of your project. I have 2 DRZs, one 2000E, BB RH valves/springs and Nova Wide Ratio that Eddie did a year ago, and a 2006 stock SM that I would like to try building myself.   I already have the ACT gears on hand.  What other special tools are recommended besides the fly wheel puller to properly split the cases on a DRZ.

 

TIA

 

Randy from Wrightwood

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Just saw this, idk of you are still thinking about it but the trail tech lightened flywheel has been known to kill stators

 

Sorry to wonder off topic...

The trailtech lightened flywheel has had issues in the past, so I wouldn't recommend one....

Anytime your after specific info try using the search feature 99% of stuff has already been covered ...

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Sorry to wonder off topic...

The trailtech lightened flywheel has had issues in the past, so I wouldn't recommend one....

Anytime your after specific info try using the search feature 99% of stuff has already been covered ...

That post was in response to the OP, I wasn't asking my own question lol. Sorry if that was confusing

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Looking forward to the successful outcome of your project. I have 2 DRZs, one 2000E, BB RH valves/springs and Nova Wide Ratio that Eddie did a year ago, and a 2006 stock SM that I would like to try building myself. I already have the ACT gears on hand. What other special tools are recommended besides the fly wheel puller to properly split the cases on a DRZ.

TIA

Randy from Wrightwood

All you need is a flywheel/rotor puller and a case splitter as far as special tools go. At least that's as far as I've seen.

I know the manual lists special tools to hold the clutch drum and for removing and installing bearings, but so far, I haven't needed any. Only time will tell though.

Just saw this, idk of you are still thinking about it but the trail tech lightened flywheel has been known to kill stators

I won't be using one, thank you for the info.

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OEM are good, that's what I use....

Add a new piston to the list to go with the new rings in your original list....It's apart is enough reason to go with piston replacement...

Oversize valves are not needed with big bore, so good thinking to stay with std valves..

Port and polish the head.????..What do you plan on doing exactly to your ports and who is doing the work?....

Tune your carb????....Has the o ring mod been done (with wire),?? that's all it may need.....list your current settings and we will see if other messing with it is required

My buddy owns a motorcycle shop and will be doing some light port and polishing since the head is already off. I've done a few car heads before as well so I'll be helping out.

Just trying to remove any casting flaws mainly and shine that exhaust side up for faster flowing gases.

As far as the carb goes, I'm not sure how exactly it's setup until I year into it. I'm sure that "O-ring mod" hasn't been done though.

I'm trying to source most of my parts through the shop's distributors as my buddy hooks me up fairly well. I think he gets parts from Tucker Rocky and Parts Unlimited. Hopefully I can get my ACT gears through him, that will help keep the coat down. If so, I might just do the stroker crank.

The other thing is valves. I looked through his catalog and all he could get were Kibblewhites (poop) and ti valves by CV4 (expensive).

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Oh yeah, as far as bearings are concerned I guess OEM it is. They've lasted this long (32k miles).

Would you guys recommend replacing all the bearings or just certain ones?

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Oh yeah, as far as bearings are concerned I guess OEM it is. They've lasted this long (32k miles).

Would you guys recommend replacing all the bearings or just certain ones?

 

Since you have it apart..... if it were me I would replace them all.

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