Down for the count

[toadstool]

Down for the count....

I have had a pretty relentless stretch of bad fortune with my Mutt, and I have not been seemingly discreet about my many complications. I am not here to place blame on the company or my engine builder.... or myself for that matter. The purpose of this post is to relay information, plain and simple. I was driving through a tunnel with a few biker buddies and decided to rev my motor to make some noise. I noticed an instant change in exhaust note and a loss of power. The front valve cover was cracked and leaking oil. I then shit my pants as I had recently spent several thousand dollars on an engine build.

My engine builder has informed me that the motor has 4200 miles on it since the build, about 3,000 more than I thought…. Time Umm, miles fly by I guess. The rev limiter was set at 6200 RPM. I had the clutch pulled in during the revving in the tunnel. My builder theorized that while the motor was revving freely and not under any resistance, it revved higher then then the rev limiter was set. The front push rod came free and literally pushed through the valve cover, of course bending the push rod and destroying the exhaust valve in the process. The rear tappet supposedly gave way and allowed the push rod to shove the roller rocker into the valve cover causing damage but not cracking it, bending the pushrod and damaging the head and the Woods .650 cam. Keep in mind I paid for over 25 hour’s labor on the heads alone. The intake valve guides were so banged up the Teflon was completely gone! And they are supposedly several thousands out of reach.. What the fuck? I feel like throwing up. The moral, don’t fuck with the motor….. ever. EVER! Or don’t fuck with the motor if you are me….. Quote: $3,000 and 45 days.

 

[Th3InfamousI]

Sorry for your lose. You seem to be taking in admirally however obviously minus the lighter wallet.

Will you be detuning this time around?

You did not have a 2 stage RevLimiter?

 

[toadstool]

I do not plan on de-tuning the motor at this time. The rev limiter was set via the thunder heart ignition; I am not familiar with a two stage rev limiter. The builder stated that he had never seen this happen in 30 + years. I wish I could pin point the issue as to not replicate it. I question the revving as the sole issue, but what do I know.

 

[woodbutcher]

my sympathy, hope it never happens again.

 

[tommy666]

Sucks brudda! Get'er back on the road and the issues behind you. It's amazing how fresh air/wind will clear the mind.

 

[BigDogBro1]

Sorry to hear about your bad luck.

Seems like your story is not uncommon and others that have attempted to modify an engine have had limited success as well. I can feel your pain and hope that you can recover some of the investment towards another build.

 

[RCAdd1ct]

This is why a vocalize issues with built engines.

If you want to do it fine, but at least they have an idea what they are getting into.

They top ended my 117 build four times before I had the 124 installed.

Improperly cc'd heads and bad parts combination was the issue with the 117.

Then when you get it right you blow up the next weakest link.

All told my bike spent eight + months in the shop

 

[Noodles 434]

that sucks. IMO a rev limiter should work whether under load or not. Personally i do not see where not being under load / being under load would make a difference if the limiter was set at the predetermined rpm limit, 6200 rpms is 6200 rpms, IMO sounds like a CYA for the engine builder. if it was me i would personally contact the company who built the rev limiter and inquire how their product works, i also would not explain the situation to them until they give an answer, and then see what they say.
Good luck with getting some resolution
As they age old saying goes, Speed costs money, how fast do you want to go?

Darryl

 

[woodbutcher]

big difference in unloaded rpm and loaded rpm. with loaded, you have the rest of the mass (ie: transmission, clutch assembly, rear wheel) to help absorb the stress. without it, the motor is on it's own. way more motors blow up unloaded due to heavy foot/hand.

 

[krkostecki]

Dude, that sucks ass. Sorry to hear about that. Looks like it's time to dust off the crotch rocket (ZX10R) - Or what I would do is sell it to pay for the Dog's repairs

 

[paulsauto]

the rev limiter cuts the ignition it does not stop the motor from spinning past the rpm with no load on engine. i would have to have a engine brake if you wanted the engine to wind up to 6200 free wheeling and suddenly stop at that rpm.

 

[spadesluck]

Rev limiter is a rev limiter. It cuts the motor out at a certain RPM's not matter what. I was under the impression it did not matter load or no load as it is set at a certain number to cut off.

I do agree with load and no load. I never thought it was a good idea to rev engines up with no load. Regardless that does stink that happend to ya. Keep your head up. It makes me sick to think about it as well.

 

[prizepup]

Damn, Jesse, I feel for you, bud. It sucks that you're having all these problems with your scoot. But we all appreciate you sharing this info with us so we know what to avoid. So your experiences aren't a complete waste. I know that's lame. Just trying to make you feel better, bro. So what's your next move? Are you gonna fix and keep her or what?

 

[Fibersnake]

A rev limiter cuts off the ignition and if loaded, the engine will start slowing down and not run higher. If un-loaded, like in your example (i.e. take the load off while increase the fuel), even when the ignition circuit is cut out, the inertia of the flywheel with no load other than interanl drag from engine, can and does allow the RMP to exceed, more so if you took it from say 2500-3000 and removed load and spun it up. It will freely go from that 2500-3000 to 6200 (where the ignition cuts off) and past it due to the inertia.

Since your removed much of the load on the engine by pulling in the clutch, the firing pressure went way down and thus the opposing pressure, thus not as much on the valves, etc. thus increasing your chances for the push rod speed to exceed the speed from opposing cylinder pressure and spring pressure and thus boom.

Inertia is amazing thing, on some diese engines for example, it happens more than most think (especially on like 2 cycle such as old Detroit Diesels) with run away. Seen more than a few lose control on genset, emergecny procedures taken, (shut off air, kill fuel, even flooded it with co2) and it just kept on going (lot due to leaking oil and self ignition) and the only thing stopping it from throwing rods and pieces was to load it up (easy to due if it is parrel with other, not so easy if solo genset).

Many UPS of flywheel types use inertia to advantage where the flywheeel are spun up to a very high rotational mass and when power is loss, that inertia will drive a generator for sufficient time with a load until genset kick on line and take such.

Bottom line never rev to redline while removing the load. You want to hear that engine going through a tunnel, dropp the gear and rev her up under load in lower gear.

Sorry to hear of the issue, frustrating for sure, but get it fixed, then get out there and ride it smartly and within reason and enjoy the many miles of freedom of the open road.

 

[MARV]

Ask your builder if he ever uses travel limiters in his high lift high comp builds.

Keeps the valve train tight at high Rpms

Less chance of valve float or the tappets not riding the cam

High rpm, tappet doesn't ride the lobe of the cam, maybe a little valve float at the same time, pushrods comes out of the rocker socket..........bing bang boom

Maybe

 

[Fibersnake]

Ask your builder if he ever uses travel limiters in his high lift high comp builds.

Keeps the valve train tight at high Rpms

Less chance of valve float or the tappets not riding the cam

High rpm, tappet doesn't ride the lobe of the cam, maybe a little valve float at the same time, pushrods comes out of the rocker socket..........bing bang boom

Maybe

That would help for sure to limit the travel, that and not pulling in the clutch for a prolong time (i.e just long enough to shift) while reving the crap out of it. Also one of the reason for certain application to stick with solid all the way and get good at adjusting valve clearance.

You doing good Marv? Best to you and the family BTW

 

[pknowles]

Down for the count....

I have had a pretty relentless stretch of bad fortune with my Mutt, and I have not been seemingly discreet about my many complications. I am not here to place blame on the company or my engine builder.... or myself for that matter. The purpose of this post is to relay information, plain and simple. I was driving through a tunnel with a few biker buddies and decided to rev my motor to make some noise. I noticed an instant change in exhaust note and a loss of power. The front valve cover was cracked and leaking oil. I then shit my pants as I had recently spent several thousand dollars on an engine build.

My engine builder has informed me that the motor has 4200 miles on it since the build, about 3,000 more than I thought…. Time Umm, miles fly by I guess. The rev limiter was set at 6200 RPM. I had the clutch pulled in during the revving in the tunnel. My builder theorized that while the motor was revving freely and not under any resistance, it revved higher then then the rev limiter was set. The front push rod came free and literally pushed through the valve cover, of course bending the push rod and destroying the exhaust valve in the process. The rear tappet supposedly gave way and allowed the push rod to shove the roller rocker into the valve cover causing damage but not cracking it, bending the pushrod and damaging the head and the Woods .650 cam. Keep in mind I paid for over 25 hour’s labor on the heads alone. The intake valve guides were so banged up the Teflon was completely gone! And they are supposedly several thousands out of reach.. What the fuck? I feel like throwing up. The moral, don’t fuck with the motor….. ever. EVER! Or don’t fuck with the motor if you are me….. Quote: $3,000 and 45 days.

4200 miles in 45 days, is this your commuter? That's just under a hunder miles a day.

 

[scubaman15]

This is a good lesson for the the younger folks on here !! As Tim and others have stated a ignition limiter will NOT keep a engine from over revving in all insistence's.
If you down shift to a lower gear and road speed is too great..yep over rev
If you miss a shift during hard acceleration and disengage your clutch at the wrong time ...yep over rev
Run your dog hard but be mindful of what your motor is doing...
Lugging your motor is also harmful but that's another post !

 

[Th3InfamousI]

Please someone correct me if I am wrong however wouldn't a two stage rev limiter not work for this application?

I understand it's over kill but it could prevent an over rev under no load. You can set the no load rev limiter to less RPM's, ie 3,000 or so. I'm just thinking for $200 bucks it might be a safe bet, can also prevent damage due to misshifts.

I still have the stock BDM 520 cam in my engine, I'm not racing anyone and no plans to start either. I may put a 585 in at some point but no rush I don't have anywhere to be that fast. Just enjoying the ride.

The Dyna DRL-400 Two Stage Rev Limiter has been specifically designed to maximize launch performance and over-rev protection in drag racing. The DRL-400 allows a precisely controlled launch rpm limit to be set, while also guaranteeing against over-rev damage due to missed shifts or drive train breakage. Selection between the launch limit and the upper over-rev limit is usually made through the use of a clutch lever switch. Both rpm limits are adjustable via two knobs on the DRL-400.

The DRL-400 constantly monitors the engine rpm with great precision and randomly deletes ignition pulses to hold the engine exactly at the desired rpm. The DRL-400 can hold a 270 horsepower engine to a steady launch rpm with less then +/- 50 rpm wavier. Other launch rpm limiters typically make the engine rpm waive through a pounding oscillation. This can be very hard on expensive racing components.

The DRL-400 works with all inductive electronic ignitions on 2 and 4 cylinder engines. It is housed in a 3 3/4" x 2 3/8" x 1" plastic case with integral mounting flanges.

DRL-400 Features:
•Accurate launch limiting with 32 different settings
•Smooth, non destructive launch limiting
•Adjustable high limit between 16 different settings

 

[toadstool]

4200 miles in 45 days, is this your commuter? That's just under a hunder miles a day.

The quote to fix the ride was around $3,000 and the quoted time frame was 45 days. I guessed that I hadn’t ridden the bike as much as my builder had documented, but I wasn’t paying attention to miles. I have had this motor for about two years or so.

Also thank you for the comments. I will relay your information Marv.