DRZ400SM Rebuild Questions

My '05 SM had it's rod bearing go out at 15,000 miles and scored my cylinder so its time for a rebuild. I already have the engine out and cases split, just getting ready to clean and inspect everything and spend lots of money. Bike as of now has 3x3, full Yosh RS3 Off-Road exhaust, and JD jet kit.

The plan so far is to get:

My main question is if I should replace the engine bearings or not. I feel like I should since I have the engine apart and plan not to have it again for a while, but its around $200 for main, transmission, counter balance, etc. I could not find anything about inspecting bearings aside from feeling smoothness. Is there anything that indicates I should replace bearings? Should they be fine? Or dont risk it and replace all since I had metal running through the oil?

Let me know what you think along with any recommendations for the build. I plan on skipping out on the stroker to eliminate challenges with compression and reliability and skip out on cams for the sake of $$$.


If the bearings feel smooth they should be ok. I personally would put new ones in.



Yeah .. I see some bad reviews lately on the hot rod cranks , I have a + 5mm HR crank it must be 6 years old . No issues but I don’t flog it at all . 

Check some reviews 

I tend to put all new bearings in as long as a motor is split ,especially the high load bearings like crank ,one behind the clutch and the output shaft , much nice to start new instead of possibly needing to tear apart again in a few years from a bad bearing . 




Alright, plan on going with the safe route and replacing bearings.

Any thoughts or recommendations on the build as far as hot rods crank or hot rods stroker?


I used a kit from BP Racing that had the HR crank and bearings , then bought the rest of the bearings from our source at work . I've not had any issues thus far but like NEKOOHC , I have mine setup for lowend and don't run it hard up top . Don't think it's ever gotten even close to the limiter to date .  IIRC the bearings were a good name brand(SKF, MRC, FAG, ect..) not some off-brand ,Chines copy (I would've gotten different ones rather than installing) , but can't remember what brand anymore.




Edited by jjktmrider

That is a kit similar , but I called them and they made a "special" kit of the parts I wanted , big bore(Cylinder Works) and piston(CP, but I put in a different one @ 13:1 cr ), stroker HR crank and bearings ,(not the whole bearing kit because I wanted to use my own sourced known brand bearings, just in case theirs weren't , ocd), Web Cams (profile of my choosing) with adj cam sprockets, and gaskets , (I still got a oem head and base gaskets ) . You can call them and do the same or buy what they have online .



Edited by jjktmrider

subbed..... this is almost exactly where I am at

Hoping more will chime in about rebuilds and parts combos. What happened to yours?

I just rebuilt my SM and used all that you are using.  I bought all Hot Rods bearing kits.  Note, the balance gears are not included.  Also, I bought a blind bearing puller off of ebay, and it was the business.  It was pretty simple to install it all and I am sure the bearings are good, new crank, piston and cylinder.  I think I am at about $1500.00 all in.  Of course I have way more than that in the scooter, but it is nice.




I'd stay away from the hot rods crank...I put one in my wife's bike and it lasted less than 1000 miles.... I've built a lot of motors ...never had one grenade on me...until now.

What went bad?

Did you contact them? They should replace it. With any product, there will always be a defective unit every now and then. Far too many good results from the bikes and quads to completely write them off.

lpmike, we'd really like to know what failed.  Maybe your wife should ease off berm busting.

Also curious about what failed. Was it the rod bearing? That's what went on my stock one that caused all this.

Also curious if anyone could chime in on the hot rods stock crank assembly. I've read so many positive as well as negative reviews. What fails on them if it is so common? And if one should truly stay away from them what are the other options besides the $600+ OEM crank assembly?

You don't really have to worry about the Hot Rod cranks , they have as good a rep as anything else . If you wanted to get really fussy you could send your oem crank out and have a Carrillo rod installed .



This is good. I too, have been hearing mixed things on the hot rods stroker crank.

On ‎11‎/‎23‎/‎2017 at 7:36 PM, 38super said:

What went bad?

Rod bearing went bad.  I didn't contact them because I actually sold the bike before it happened. The guy that bought it rode it for a short time and it grenade on him!   I felt really bad and sent him $400. to help with repairs. Hopefully the head is ok...I'll probably never hear back from the guy...he's not too happy with me. Whole thing kinda sucked. :(. When its time to do my other DRZ I'll be going with the OEM crank. Like I said...I've done at least 20 bottom end rebuilds over the years on various bikes...and NEVER had one go bad.

There's the "rest of the story" , unless you actually were riding it there is no way to know how the guy was riding it , quite possible he had it bouncing off the rev limiter for 20 miles .  Any complaint I hear from someone coming from a third party and wasn't even there when it happened I toss it out as BS .  I've sold 2 things in the past that the new owner blew up(Honda 250R) ,one that very night , the other the first weekend he had it(396 chevy big block) , both insisted they did nothing and both I found out through friends or the one sister that they were beating the holy shit out of it at the time .




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