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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Stethoscope.. Compression and leak will only show issues if rings / cylinders are effected.. Listen carefully for where the sound is loudest / sharpest.. If it's a pin / piston / upper rod issue, you'll hear the dink when you poke between the fins.
bwoltz is right but compression and leak down will not only show ring/cylinder issues but will also show the top end is in good condition as well. Not bad information to have for future reference for a DIY guy.
Using a stethoscope, I'm even more convinced then I was before that its a lower end noise. No real noise from the cylinders, and the slight noise I heard was consistant front to rear. Noise was significantly louder the closer I got to the cam chest, touching a timing cover bolt it was really loud.
I also bought myself a compression gauge, not sure why I'd never bought one before, but now I have one...
Front cylinder was right at about 180, and rear about 185. Whenever I see someone post their compression readings, they're generally 200-210. Is that unusual?
To add a bit of backstory, I've never had a proper dyno tune on the bike. I'm running a Thundermax, and while the bike to me has always run really good, it wasn't putting out the kind of power I expected. I ran it on a dyno once at a local bike event and it maxed out at 88hp and 98ft-lbs torque, which is less than I was expecting. I've also been getting some pinging on heavy throttle, which I've maybe improved a little bit by playing with the timing, but I really need to have it tuned professionally, and I can't find anybody around here that will work with a Tmax. I've been seriously considering switching to a different tuner, but that's a different subject.
To recap my engine setup: '09 96" with a 103" SE piston/cylinder kit, Wood 555 cams, WFOLarry Stage 1 heads w/stock valves, .030" head gaskets, D&D FatCat pipe.
I'm going to continue on with my plan of pulling the cam chest apart and seeing what I find.
Last edited by Reindeer; Nov 26, 2016 at 05:03 PM.
I'll be good if the problem is in the cam chest.. Might be something like a loose sprocket on the crank..
If you are running flat top pistons with that build and Larry didn't whack much off the heads, 185 is probably close..
On the Dyno I used to use your HP and tq numbers are probably not that far off, especially without a tune and it looks like both the dyno and bike may not have been completely warmed up.
Be sure to check crank runout ..... VERY possible source of the problem ... esp. with performance mods you've made ....... Good Luck ... hope it's something simple .....
I thought about it after my earlier post regarding compression, makes sense since mine is essentially a stock 103", and most #s I probably see listed are for performance built 107s or bigger.
I'm going to try to dig into it a bit in the next couple weeks so I can formulate a plan. I'll post an update once I get the cam chest apart.
My bike was making a light buzzer sound from the cam chest, like a buzzer on a dead battery.
After opening it I found metal, a bearing has come apart. Really sucked too...
Good luck... hope it's a simple fix.
Finally had some time to pull things apart. The oil pump and the bushing on the cam plate look fine to me. The crank runout is about .004, which is where it was when I checked it a few years ago.
Looking everything over in the camchest with my untrained eye I don't see anything unusual. Very minor scoring on the end of the crankshaft snout, goes a little less than 1/2 way around, but smooth enough I can't catch a fingernail on it.
I kinda assumed I'd see something apparent, and now I'm not sure where to go. Could it be a bearing issue? I wouldn't think roller bearings would make noise.
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