Another reason why HD sucks.

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A few years back I helped a friend build up his '05 883 sportster. We put in a 1250 kit from NRHS, he sent his heads out to some HD guru for full porting, OS valves, springs,etc. Mikuni HSR, ignition, exhaust, etc... turned out pretty quick but still not as fast as my nearly stock vmax.

Fast forwar to a couple weeks ago: I get a txt saying he thinks he blew it up. We talk and I tell him to check a few things. Long story short, the pistons smacked 3 out of 4 valves and bent them to shit and 3 push rods look like bananas.

The cause you may ask? A cheap ass woodruff key sheared on the crankshaft! The woodruff key is shared by two gears to locate them on the right side of the crank. One gear is the oil pump drive, the other is the pinion gear which drives the cams. 80% of the key touches the oil pump gear. Only about 1/8" of the key stick out beyond it to locate the pinion gear. That tiny 1/8" nub sheared off. When this happened, the cams got out of time and got smacked hard. I guess the key didn't like the added pressure of more aggresive cams, stronger springs, and heavier valves.

I searched around about this and found it to be somewhat common but did not find a good fix. I did find a tech article from NRHS saying the best way to combat this is to put red loctite on the pinion gear bolt and torque it to 70 ft lbs.

Check out the attached pic and note the tiny nub sticking out past the oil pump gear on the shaft. This is what locates the pinion gear. Must be a lot of pressure on that little nub!

Sent from my SCH-I405 using Tapatalk 2

 

[Miles Long]

Agree and possibly disagree.
True, having only a fraction of the key supporting the pinion gear seems like a basic design flaw, but when you did your research, did you find this was a common failure mode of the stock engine, or of engines upgraded with the HP- raising components?
If the latter is true, I don't think it's fair to blame HD. The engine would not have been designed to handle the added induced stress of the upgrade.
Just my opinion
Cheers!

 

[AMechEng]

That sucks. Next time go with an S and S.

 

[bazwell]

What a piece of rubbish! :rofl_200:

Oh well.
How would it go if you got the oil pump gear narrowed down 1/4" and moved the other gear further over the key? That would make it 3 times as strong!!! (as long as the gears didn't foul etc etc.)
Or extend the keyway and use a longer key, if he's willing to take the crank to a machine shop.

It's possible that the bolt comes loose sometimes (the cause?). So the loctite fix might *just* hold it together normally. :rofl_200:
Maybe spinkle a little bit of magical pixie dust on it too...
and tighten it when the moon is full...
on the spring equinox...
with a virgin socket...
under the guidance of the local minister...
on holy ground...
with your fingers crossed.

I keep thinking "I should get a nice simple slow old Harley that you can buy parts for", but then I see engineering like this. Fashion comes at a price! :rofl_200:

 

[dtoebaert-5311]

80% of the key touches the oil pump gear. Only about 1/8" of the key stick out beyond it to locate the pinion gear.

They sure got their priorities right! :rofl_200:

 

[06VMAXIMUS]

That does suck. The HD guru who built it should have known the possibility of that failure happening when getting aggressive with the mods. That area should have been addressed by him, IMO.

 

[[email protected]]

Agree and possibly disagree.
True, having only a fraction of the key supporting the pinion gear seems like a basic design flaw, but when you did your research, did you find this was a common failure mode of the stock engine, or of engines upgraded with the HP- raising components?
If the latter is true, I don't think it's fair to blame HD. The engine would not have been designed to handle the added induced stress of the upgrade.
Just my opinion
Cheers!

It is more common on bikes with bigger cams, stronger springs, bigger valves. I did find a couple cases of basically stock bikes doing it also. Modifying engines for any application seems to be a game of compromises for most any manufacturer. I just thought this seemed to be a weak point in the design.

Reminds me of the vmax orange o-ring. Something that could have been better designed from the factory.

 

[old timer]

EVERY brand has their strenghs and weaknesses , bikes , cars , boats and even toasters...:confused2: Harley , along with every other manufacterer deserves the shit they get BUT dont forget they build in obsolecence so they can sell parts...

 

[[email protected]]

EVERY brand has their strenghs and weaknesses , bikes , cars , boats and even toasters...:confused2: Harley , along with every other manufacterer deserves the shit they get BUT dont forget they build in obsolecence so they can sell parts...

Agreed. I had to go to target a few week ago to replace a toaster I received as a wedding present. :biglaugh: First time I ever had to buy one.

Vmax has its issues too. The o-range o ring for one. The bearing surface built into the block is another weak point IMO.

I'm not a HD hater. Got plenty of friends and relatives with 'em and we all ride together and take jabs at each others bikes all in fun. I just thought it was a pretty shitty design and was surprised that there seems to be no readily available option to improve upon it considering that it does not seem to be a rare occurance.

Also, I know there a few guys here that have XL's or XLC's. Figured it may raise awareness of this issue and save some guys a few bucks. Doesn't really cost anything to open the cam cover and loctite 'n torque a bolt. If it saves just 1 engine from being thrashed I feel that I have completed a public service :biglaugh: