Throttle Plates NOT flat at WOT - 300 HPDI

[lockhah1]

Gents,

Z300 TXRC - How do you replace the throttle cam collar (PN 65L-14578-00-00)?
Any tricks to it?. Mine has a flat spot in it.

Issue - the throttle plates are not completely flat at WOT. There is play between the cam and the collar at WOT - they are not even touching. In fact, I can push down on the accel. level rod (PN 65L-41217-00-00) about 3/16 in. and make the throttle plates go flat. Lets assume link and sync is spot on. Engine starts and idles great with no issues throughout the whole RPM range.

Any thoughts, ideas!

[rodbolt17]

cut or pry off the collar.
snap the new one in place.

[lockhah1]

Thanks rod. Here is a pic of it. Flat spot right about 6PM. I take it by your reply, you have seen this before. What are the chances that the cam groove is worn also? After all is plastic as well.

[pstephens46]

On an IPhone here. Having trouble making part number match on the Z300 txrc on Boats.net. You want to replace grey or the black cam assembly? Didn't realize that was much of a "wear" part. Hopefully Rodbolt can provide more details. Easy to separate the two.

So you ran the motor at WOT in the water with cowl off playing with those parts to determine the problem? I probably would too....

[boscoe99]

Usually it is the cam roller that wears or is flat spotted.

682-41291-00-00

[lockhah1]

Hi Boscoe,

Is that a P/N for a Z300 TXRC? Mine don't look quite like it. Attached is a pic of mine.

Hi pstephens46,

Not in a million years! This I noticed when performing a link & sync a while back (with the intake silencer off). I wish I would have never looked in there. It bugged me ever since. Z300 are getting scarce now days and I can't find another one to compare with.

I can't understand why the plates are not flat at WOT even though I'm getting plenty of throw from the cables (already checked that). The only thing that appears to be out of wack is "play" that exist between the roller and the cam groove at top of travel, i.e. WOT. We are not talking a lot of money here...maybe $50 tops on both parts - but I hate to throw money like that without having at least some certainty this may be the cause. Thus the reason I'm asking the guru's of this forum for help (as I have before and very much appreciated it). Thanks!

[rodbolt17]

most likly cause the plates never go flat(horizontal) at least not that I have ever seen on an HPDI.

[lockhah1]

Rodbolt,

Thanks for the insight. Looks I was chasing a ghost. All carburated motors I had before, the throttle plates did go flat at WOT.

While searching the web last night, did come across a case where the throttle plates on an F225 fell short of going flat by design. I can't rememnber exactly the particular models/years, but the OP was asking for the differences between an F225 and F250. Apparently the ECU was different as well. Like anything you read in the web - it may or may not be truth.

Early in 04-05 Yamaha made some "dealer" modifications to the Z300 HPDI. The famous water intrusion kit was added as well as a change in ECU and oil pump. I can confirm the dealers mods were performed on my motor. Last night I started thinking IF my issue with the throttle plates had to do with these modifications (before I saw your response this AM) - derating the Z300 to increase reliability perhaps. Do you know?