How many had their throttle plate shaft break?

[tdrglide]

My HPI 51mm throttlebody has a larger diameter shaft than the stock Delphi throttlebody. Also bearings instead of bushings. Should hold up better, I hope. Mine (both delphi, one stock and one that had been bored to 48mm) broke at the screw on the tps side. Luckily the screw  stayed in the throttle plate both times

[les]

My HPI 51mm throttlebody has a larger diameter shaft than the stock Delphi throttlebody. Also bearings instead of bushings. Should hold up better, I hope. Mine (both delphi, one stock and one that had been bored to 48mm) broke at the screw on the tps side. Luckily the screw  stayed in the throttle plate both times

The larger shaft and bearings instead of a bushing type support at the mods that HP Inc are currently making to my MMXF.  Appearently, HP Inc (as I saw on the shelf) is available to make these mods to stock Delphi EFI's.  What was interesting is that HP Inc showed me the slotted shaft style (mentioned above) but said that this design still had problems and the larger shaft with the bearings is the solution...or at least the latest design idea.

[tdrglide]

I should say, HP Inc. did not do the 48mm bore mod for me. It was somebody else.

[DblackmanC]

Les...You got me to thinking and looking. I went out to my '06 (49,000 miles) and checked shaft...No problem now nor have I had one. (yet!) The '06 has the flat side, no slot. Looking at the pictures above it appears something is twisting the shaft at the weakest point. We all know the side with the cables will be turned by our hands as hard as needed. Something would have to be in a pretty bad bind to twist the shaft OR could there be some kind of a problem with the TP (throttle sensor) that the shaft must turn on the other side?? Some kind of bind in that unit would do what we are seeing..right? I don't know how that unit hooks up but sure looks like a place to start! I've seen much smaller throttle shaft work just fine but not with this sensor on the end. Thinking out loud!
Dan

[fxstdavew]

I wonder if servicing the throttle body to remove coking that accumulates around the shaft and plate may help. Coking would be worst if the breather is still going to the TB. After cleaning a small shot of lube at the bushings too. 

[les]

Dan, from talking to HP Inc they say that the throttle plate wacks the throttle body.  They say that repeated strikes is what breaks the shaft.  I thought the same thing as you.  "Heck, this thing is not load bearing, how could it break the shaft?"  But it appears that the repeated strikes on the plate eventually crack the shaft right where the bolts screw in...that's the weakest part.

I just got my EFI back from HP Inc.  The new shaft is bigger.  It is not slotted, rather a flat on one side like the old one.  Lot more stock and should be more durable.  Also, they installed bearings to support the shaft.

No matter who tells you, don't ignore this situation.  Even if you do nothing about it be aware that a broken shaft could be right around the corner with a bolt sucking into your engine.  The purpose of my post was to find out if others have experienced this and the postings are a testamant to that.  It has and it does happen!  That is a fact.

[CraigArizona85248]

The throttle shaft is actually under a considerable load.  Especially at cruising speeds where the throttle plate is not open very far.  You get rapid fluctuations in the pressure inside the intake manifold as the intake valves open and close.  I would imagine this constantly changing pressure beats on the throttle plate pretty hard.  I can see how it could weaken a throttle shaft over time.  The broken shaft LilEvilAmy showed is exactly where I would expect the shaft to break.  Definitely the weakest spot.

-Craig

[tdrglide]

I know it looks dirty, but it still should not have broke. After this one broke a local shop offered me a free take-off he had sitting around from somebody who changed to carb. We took a close look at it and it was cracked at the same place, ready to go. So I knew it wasn't just me.

[attachment removed after 60 days by system]

[DblackmanC]

Les
I'll make this a inspection item every week or two now!
What did it cost to have your TB modified?
Thanks,
Dan

[les]

First of all, I'd like to thank Craig for pointing out where another source of load may be coming from.  Makes sense.

I didn't have to pay anything for the modification. HP Inc. (like companies such as Baker) stand behind their products.  HP Inc repaired their unit at no charge.  Not sure if they will do such a modification though if it's not in a broken state, and I'm sure they would charge for an H-D Delphi unit.  Just not sure how much.

[les]

BTW, the picture in posting #32 is exactly what I saw with mine when I took the air filter off in the parking lot of where I broke down.  Exactly, except for it was the other bolt.

[Bluedresser1]

04' Ultra. Mine went at 40K.

[ViennaHog]

Outside atmospheric pressure and inside very low pressure during decel from high rpm creates considerable force on the plate and and resulting torque at the shaft. too lazy to calculate it...........

[f-x-d-w-g]

Shouldn't a TB with a broken shaft be covered by the emissions warranty?  IIRC that's good for 5 years.

[les]

04' Ultra. Mine went at 40K.

That must be the average time, because mine went in that many miles.  So, maybe equating it to cam chain tensioners.  Seems about the same lifetime to start giving this serious consideration.

[ViennaHog]

04' Ultra. Mine went at 40K.

That must be the average time, because mine went in that many miles.  So, maybe equating it to cam chain tensioners.  Seems about the same lifetime to start giving this serious consideration.

Could be the designed lifetime of the bike......

[hdtuner23]

Glad to hear though that HPI is a great company that will stand behind the products they make!  Many factory MOCO shafts I have seen break, warranty, I think not. Not even a repair! You must purchase an entirely new t/b, only $345.00  Good luck on your future riding!

[FLTRI]

Yep, the 8 broken throttle shafts on our "dead meat" shelf from early delphi EFI TBs probably never happened. So are the 2 HPI shafts that broke.

Personally, while travelling south to LA with 22,000 miles on a 95ci 2003 RG the engine had started running erratic. When I got to LA I went directly to LA HD. The Service manager had one of the shop mechs pull the A/F off and low and behold the throttle shaft was broken.....into 2 pieces. It still would move the TP sensor, just erratically.

I asked him how he knew to look there first. His statement was: "This is not our first rodeo with broken Delphi throttle shafts".

At that time anyway the MOCO did not service the shaft separately but LAHD stocked a couple TBs for replacement.
2 hours later I was burning gas again.

Since then (2004) we've seen and replaced more than a couple few broken shafts both on Delphi and HPI TBs.
Only seen one broken shaft on a stock bike, most being on over 95hp/tq build bikes.
Could be my imagination but the customers are convinced.
Bob

[les]

Thanks Bob.

[L-]

So, what is the single best cure/fix for this before it happens? Bigger shaft?

L-

[fxstdavew]

At that time anyway the MOCO did not service the shaft separately

Is there a service kit available now? If so how much, Part# ?

[f-x-d-w-g]

There is no service kit for the stock TB as of 2 years ago.  It's sold as a unit for $76 ) TB only, no intake manifold, injectors, or sensors.

[fxstdavew]

76.00? It's not as bad as I thought it would be.

[FLTRI]

There is also a plethora of stock TBs available on eBay, Craigs List, indys and dealers, etc for cheap.
Bob

[les]

So, what is the single best cure/fix for this before it happens? Bigger shaft?

L-

I think one option is to have a company like HP Inc perform the modifications (bigger shaft, shaft bearings).