5th Gear Wear, Spalling

[dp]

I'm slowly getting my project engine together for the 84 Interstate. Inspection of the transmission mainshaft 5th gear (35 teeth) shows pitchline wear (spalling) on about 12 of the teeth. The partner gear on the countershaft shows no visible damage. The internet suppliers list this gear as microfiche item #21 with Honda p/n 23481-MG9-010. The bike only has about 65,000 miles, so I'm guessing that at some time in the past, dirty or contaminated oil got the problem started. Has anyone else come across this problem? Thanks for your input.

[SIR tricky]

Maybe Vic might help with this one, I don't think many of us would venture to split the engine, I think most are of the buy from Ebay and replace group.

[dp]

Please let me add additional info; I have taken the transmission mainshaft to the dealer so they can pull off the forward end ball bearing, replace the fifth driving gear and press on a new ball bearing since I don't have a hydraulic press. More critical inspection of the countershaft 5th driven gear does reveal some very small pits on a few of the teeth. My problem with that is removing the two (2) countershaft bearing cap phillips screws. My old manual, hammer driven impact wrench has broken two #3 phillips bits trying to get these screws out so I can slide out the fifth driven gear. I think my next choices are a little bit of flame to heat up the area or turning this over to the dealer also. Any wisdom from out there would be appreciated.
Thanks,
Dennis Price in MN, USA

[Guest]

What I have done is take just the bit without the driver, place the bit in the screw head & strike the bit a few good hits. Then try the bit with the driver again. Poorboy

[Ed Z]

Another trick is to put the phillips head bit into a socket that fits it... Now fit the socket onto an impact wrench (electric or air)... It's quite surprizing how well this method works...

[dp]

Poorboy & Ed, thanks for the tips. The bit & hammer did the trick. I got the countershaft out for a close inspection of all the gears. There are some small spots of pitting/spalling on the inboard edges of many of the 5th gear teeth, so I will be replacing this gear along with 5th gear on the mainshaft. Given that the bike runs in 5th gear 99.9% of the time, I can't see going back together with any damage on either gear.

[dp]

Now the Honda dealer is telling me that the mainshaft 5th gear is no longer available from Honda. Guess I will have to search out new old stock or some used gears. Does anyone have a lead for me to follow? Thanks.

[catman]

Well I would say I would sell you my spare but...that may mean I would be SOL down the road.
try Karl or one of the others on my poor excuse for a web page:
<!-- m --><a class="postlink" href="http://catman01.webs.com/">http://catman01.webs.com/</a><!-- m -->

[Guest]

Hi, check at Whitey's Classic Wing. I am pretty sure he has what you need, the link is:
<!-- m --><a class="postlink" href="https://id212.chi.us.securedata.net/whiteys-classic-wings.com/merchantmanager/index.php?cPath=2_43_112">https://id212.chi.us.securedata.net/whi ... h=2_43_112</a><!-- m -->

Good luck with your project.

Claude from Ottawa, Canada.

[wingandaprayer]

dp

I am not much help to you to find parts - but spalling of the gear sounds suspiciously like non motorcycle spec oil being run in the engine/trans unit - I am only speculating - check out the "motorcycle white paper" on Amsoil's website - there is some excellent technical information in the paper on why bike oils are formulated the way they are - and a number of results of SAE tests on a number of motorcycle oils. You can pick the one that suits your bike use and storage the best kind of thing. You will put lots of work, time, and some $$ into your project - which is all part of our sport - all the best with it.

<!-- m --><a class="postlink" href="http://www.amsoil.com/products/streetbikes/WhitePaper.aspx">http://www.amsoil.com/products/streetbi ... Paper.aspx</a><!-- m -->

[dp]

Thanks guys, you've given some great input. I believe I have a full transmission, mainshaft and countershaft, coming through "Fleabay". However, it is from a 85 instead of a 84 like mine and I know the overdrive ratio is different (28/35 versus 29/35). My hope is that the 84 shafts/gears will pull out and the 85 shafts/gears will drop right in with no issue. Do any of you have experience with this kind of swap out? Thanks.

[admin]

As far as I know the 84 and 85 gears are different ratio wise and the primary drive ratio is also different but maybe you'll surprise me and tell me that they are the same after you get your parts.

Regarding the spalling, I have seen the same thing happen to an 87 GL1200. The problem there was determined to be that the PO was using standard 10W30 car oil and did not change the oil often.

[dp]

Yes Vic, there are ratio differences. My information indicates that between the 84 & 85, 1st gear, 5th gear, and the secondary reduction ratios are different while 2nd, 3rd, 4th, and the primary reduction ratios are the same. I have procured an 84 transmission (had the same 5th gear spalling), an 85 transmission that can be used, and another 84 gearset on the way. I would prefer to swap 84 for 84, but I believe the 85 will work if I slide on my good 84 secondary reduction driving gear (aft end of the countershaft). The other option is to just install both 85 5th gears on my 84 shaft assemblies. If I use the 85 with my 84 secondary reduction, I will have a little more overdrive. My rough calcs indicate about 100 rpm less at my cruising speed. I guess the condition of this next 84 transmission will make up my mind. I'll try to attach a photo of my bad 5th gear. Any advice or input would be appreciated. Thanks.

[admin]

Just my opinion but I would wait for the correct 84 parts because I feel that you would notice that 100 RPM drop just a little too much. Not saying it won't work, just saying that the 84 parts would make it work better.