SV 650 Motor Dies--help with diagnosis

RIP 12/17/2006---The SV died, well sorta. I havent torn it down yet, did a simple compression test. Here is what happened. Going down the straight at Roebling, the bike died, but still ran, making a light tapping noise. It sorta just went flat with no power. The bike has the two suzuki intake cams, ported heads, hyabusa pistons and 2 layer head gasket. It still runs and idles and revs, but you can hear the noise and its not making the power it did for 4 laps, it was moving NICE. Anyway, the compression test showed the following, and it varied a little on the readings on two tests:

Front: 165-170PSI (11.5 kgf/cm2 -- on 2nd test)
Rear: 145-150PSI (10.5 kgf/cm2 -- on 2nd test)

The Suzuki service specs in the manual for 2003 SV650 are:

Standard: 213PSI (15kgf/cm2)
Limit: 156PSI (11kgf/cm2)
Dif btw cyl: 28PSI (2kgf/cm2)

Obviously the rear is well below the service limit and the front isnt far off and well below the stock numbers.

The bike made good power. 80.8HP / 48.5ft lbs torque, on a dyno that reads a little low, by a few HP. The bike was dyno run and custom mapped.

Would it be a valve? But I would think with a valve, it wouldnt show any compression on the cylinder with the busted/bent valve. Would the problems be with the cam timing? Maybe off a tooth? But I triple checked that? Is it a problem with using the two Intake cams? It was harder to start and you actually had to hold the throttle back a little to get more gas in while cranking, its a FI Bike, but it would start and run fine. It ran real well, much better than my SS bike and the power WAS noticably better than the stock bike.

I was also thinking crank bearing, but would that make it just loose power like it did? And it sounds more in the top end. It happened in high rpms in 6th gear, and like I said earlier, it died, like it took its last breath and just went flat.

I will be pulling it apart, but just trying to get an idea of what some experienced guys think might have happened.

Thanks for any help.

 

Sean - was this the first time you were riding the built motor?

 

sounds like the end of the crank has cracked but not broken off completely. i had one of mine do the exact same thing. had power, would start up, crank was cracked where they all break. pull the inspection cover and turn the crank over to see if it wobbles.

 

Yes Ed...built the 03 over the past few weeks and have a 07 on order so I decided to get more power for SB and F2 and build the 03.

Kris..the I took the crank bolt cover off and was turning the motor over at the track checking to see if perhaps a cam might have jumped, the bolt turned fine and wasnt wobbling..felt fine. The cams were still in check, the same as they were when installed.

 

Did you build it yourself? If so, you've got balls, building one of those yourself.

Seriously though, if it's not the crank or the rods (the more common failures), hopefully it's just a valve or something minor. See if Zoran jumps on here and posts.

 

Yeah E..built it myself. The top end isnt so bad, I honestly think its somthing that has to do with using the two intake cams and valve crushing ...

 

nothing to do with cams if installed properly.
check if you broke retainer.

 

Hey Sean,
I agree with TWF2. Probably not the cams, but sounds like something in the top end. If you broke a valve stem retainer, it would probably make a lot more noise. The valve would likely go into the cylinder. Pull the valve covers and look at the valve train while you turn the engine over. Rocker, or rocker boss, valve spring maybe broken. If something in the valve train broke and the valve was not opening, you'd still get compression, just no power. Good luck.
Pete

 

It was more than a light tapping noise. It was rattling pretty loud. Wouldn't you lose all compression if you broke a retainer and dropped a valve?

 

If you broke a valve or retainer and dropped the valve into the cylinder, you'd have no compression, but it would make alot of noise. If something in the valve train breaks, and a valve does'nt open, you still have compression, but no power, and not too much noise, depending on what broke. Still just a guess.

 

Cam chain adj. backing out will make one hell of a clatter.

 

Thanks guys, heads are off. I checked the valve clearance, a little tight. I pulled the buckets over the valves and looked at the valves, my valve spring tool wont do the cycles, all the valves seemed good. I drained the oil and it had a copperish/bronze color to it. Nothing sticking to the magnet on the drain plug. It looked like very very fine particles in the oil. didnt look like anything I had ever seen when draining the oil in the past. Would a spun rod bearing cause compression loss? I know it would make noise.

 

Cam chain adjuster is fine. I have heard them before. All the cams were still set, chain had tension.

 

copper material in oil is a spun bearing. Split the cases and that's what you'll find.

 

I agree with davetlr, though the symptoms sounds like what a friend of mine had happen, he broke the crank in half, however it broke right underneath the rod. therefor the rod clamp held the crank together, the thing made no power but would start though it made a consistent clikity clak. so I would say its one of those two. At first I agreed wit Kris, I have heard of that happining a bit, crank not totally snappinf off, but if the nut isnt wobbling than maybe it broke under the rod. But again, most likely a bearing.

 

Sean, there is a possibility of a valve being barely tweeked. That would cause the clearance to open up enough to make a ticking noise and also cause it to be down on power but still run.
I don't know offhand what the cam specs are for the cams that you are using so I don't now how close the valves are to tangling with each other under normal use. When you installed the cams did you just line up the timing marks or did you actually degree each cam?

 

take cylinders off and see if rod bearing is gone.grab piston and pull/push up/down.it will move if bearing is gone to point it knocks.
also take plug on bottom of engine off,the one oposite side of oil drain.you will find bearing pieces there if gone.

 

agree...rod bearing.

splitting cases is in your future.

 

the valve train being tweeked or whatever that means has nothing to do with a spun bearing that leaves copper residue and shavings in his oil, the cases need split and further diagnosed from there. By the sounds of it he has a pretty good idea on what's going on with the valve train.

 

few things from your limited notes...

1. do a leakdown. honestly i hardly check compression, this will vary too much with cam timing and profiles..do a leakdown. It should be on a twin 2-3%..if more than that you can put some oil in the intake/exhuast ports and then check leakdown..watch the oil to see if bubbles...bent valve (bent valve will show HIGH leakdown!)

2. intake cam on ex. side? oye..never understood that... too much lift for my taste and i have seen amost nil hp gain for the work.

3. 81hp is low. I get 81-83 in Supersport legal (stock cams, pistons, no head work) with just 50% VP U4. (my dyno reads 71-72 with full m4 but bone stock motors)

4. if the crank broke, youd KNOW IT!

5. i would look at the tensioners...they are junk oem. instal some ape or similar manual ones (be sure to seal up the rear one good!!)

6., check the pigtails on the coils. the primary wires are NOT crimped very tight from factory and we have had them vibrate loose..but then again it wont cause it to tap..but it would knock cause its not firing the mixture and such..

7. if you check the valve clearences (this will show you bent valve also!) and the tensioners, and the leakdown and all is good...id check the rod bearings! Alot of times you spin a rod bearing it will knock, lose power and such...then when it cools down later next day it will start and sound ok..but once back up HOT (oil temp..not water temp) and loaded (on dyno) you will hear it again...9/10times its the front one.

Good luck. I have built over 50 SV650;s and won 18 class championships with them...just fyi since alot ask how i would know...Let us know what you find.

-Eric