DR-Z Post Mortem, Some Good, Some Not So Good

Well, I got a little time this morning and my friend Jim and I popped the head off of the DR-Z. It was pretty quick work we were done with the tools cleaned up in 1.5 hours. I also did a bad thing, I popped a keeper using the internet socket method. We wore safety shields and glasses, two smacks and we were clean. It was fun, but I wouldn't have tried it on a non-bent valve.

So, on to the carnage.

First we pulled the cams and the bucket of the destroyed Intake valve. It appears the springs failed, then the valve became unattached and walked around. We found all of the keeper and the pieces of the valve guide. What I think saved most of the stuff was that it caught the exhaust valve and the engine shut off immediately, and the intake valve made minor contact, but didn't fall in because of the exhaust valve. Lucky me. Note, it does not have Ti retainers as I was told. I will measure the valves later to see if they are stock or +1 mm on the intakes.

Anyway, on to the carnage....

Under the bucket view



BOTH! Springs failed!



Mr. Exhaust valve had a bad day as well...



It is amazing it did not obliterate the motor. Good thing I was at like 3k RPM.



It does have APE spring seats.



Piston was mildly abused, I think I am lucky there, that it isn't worse. You can see the pieces of valve guide sitting on the piston...



I think the head can be salvaged, it has almost a ding on the intake, but it is pretty shallow and might be fixable...



I have no clue if I can use it, it looks to be almost into the seat



The cylinder isn't hurt, but I think I will replace it, the piston, the crank, all the lower end bearings and seals. That way I will know what is in there. If I can't use my head I will buy another one. This one has my name engraved on it.



See on the right, my name is engraved



I can't get the intake valve out because it is mushroomed so badly. But I got the exhaust valve out and she is also a wee bit bent...





Well, there you go, sad but not so sad. I need to figure out what parts I need, I will miss the little bike until it is fixed. I am going to make her a big bore again, I might even put in regular stage II cams and sell my big ones. I am wondering if the springs were really right for those....

WOW - that must have been quite an incident!

Great photos and descriptions, but the best line in the write up is:

If I can't use my head I will buy another one.

Click to expand...

I have never seen valve springs fail like that, what kind of lift is the cam running? Unfortunate that the springs broke, but as you say quite lucky the damage was not a lot worse. Best of luck

Gary

Jeff S said:

WOW - that must have been quite an incident!

Great photos and descriptions, but the best line in the write up is:

Click to expand...

Amazingly it just died and would not start. I guess the valves got stuck almost immediately and it lost all compression.

I saw the head line when I posted it, but I thought folks might enjoy it.

OldTLSDoug said:

Click to expand...

above are the specs on my stage II hot cams

Below are the current Stage 2 Hot Cam Specs

IN .357 (9.07mm) lift 238.5 duration lobe centers 107.5
EX .357 (9.07mm) lift 238.5 duration lobe centers 107.5

So not too bad

Not enough spring? A good machine shop should be able to clean that head up.

Sent from my SAMSUNG-SM-G891A using Tapatalk

None of the after market springs have gone without a failure or two.
On my DRZ's
I lost a Mega Cycle spring, broke the outer spring.
I have a R&D Ti top split
OEM spring fail
There have been failures in every after market spring brand I know of, more so when you add in higher lift cams and RPM.

PSI makes springs that can be used on the DRZ, pretty good Rep..

Do OHC springs walk like push rod motor springs?

I don't know, I read a lot about spring height, coil binding and valve weight today. I think it is bad luck. I guess I didn't mention I have a true E-Model Ignition box with a higher rev limit that stock. They said with 500 extra RPM you can increase load on the spring well past it's designed (normally) force. So I may have had this failing for a while. The sputtering was clearly the intake not making the trip or bouncing off the seat. I think the other day, the second spring broke and the results are shown above. I needed a project for the summer. I am encouraged about the head, so it may end up just being an exercise in spending MY MONEY....

OldTLSDoug said:

I don't know, I read a lot about spring height, coil binding and valve weight today. I think it is bad luck. I guess I didn't mention I have a true E-Model Ignition box with a higher rev limit that stock. They said with 500 extra RPM you can increase load on the spring well past it's designed (normally) force. So I may have had this failing for a while. The sputtering was clearly the intake not making the trip or bouncing off the seat. I think the other day, the second spring broke and the results are shown above. I needed a project for the summer. I am encouraged about the head, so it may end up just being an exercise in spending MY MONEY....

Click to expand...

Darn bad news indeed. Will this be the first project in the new shop?

Well I guess if mine better go south I know who to call. Keep us updated

I am hoping it will get done in the new shop, if not I am going to be awful cramped in the old one.

By the way the cross hatching in the cylinder wall looks perfect. How many miles on the engine when this happened? What oil do you use? Lastly what type of break-in procedure did you use, soft, hard, factory recommended ?


Sent from my iPad using Tapatalk

I gave it a couple of heat cycles at idle until the fan came on. Then changed the oil, rode it like I stole it banging off of the rev limiter. Installed the piston rings dry with a thumb-sized dollop of oil on the skirt. Probably 2500-ish miles. To be fair, most of it was banging off of the rev limiter high RPM racetrack stuff. So, I think it was just bad luck. Looks like it will all come together. I ordered all the parts to completely rebuild (even the piston/cylinder will be replaced) and I am $1500 into it, still waiting on the price for the head. Still cheaper than a used motor, then rebuild. So I am pretty sure it will be stone reliable and as fast or faster than when I started. Probably need a new clutch too, didn't think of that, I will measure it up when I disassemble her.

A bonus photo of 1.5 valve keepers, the other part was in the head.

Good news! I found out Mr. Cylinder head will be fine, I am having it done at A.P.E. Big Bore Thumpers in Rosamond, Ca. Jeff there tells me that they will recut the seats, surface the head, install all new guides, valves, springs and retainers for $433.00 plus shipping which should be about $20.00. He told me my shims are too small and were rattling around in the valve retainer and they are torn up as well. So, something else to source. Woo Hoo! Light at the end of the tunnel. All parts will be made by A.P.E. so they should do well with my abuse. Unfortunately the intakes are not +1mm as I paid for in the past, rather they are stockers. Sad to get screwed for $600.00 on a cylinder head, but life is hard, and I learned the lesson....again!