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Discussion Starter · #1 ·
Well, title says it all. 01 vn750 with an 05 engine, (original engine threw rod bearings and tore up the rod, and the crank, but I was an idiot and didn't save the rest of the engine, bought a whole 05 for $600, minus the carbs, swapped it in, and 3k miles later here I am) noticed some knocking, thought I was losing the rod bearings again, decided to try and save myself some money, take the bike apart before it gets worse, and I might be screwed again,

The problem:
Right side crankshaft bearing spun in the case, the crank is good, thank God, but the aluminum case has some gouging, could easily be machined out, but I know these cases act as thrust bushings for the crank, so would machining it take away this aspect? And would I be alright running a thicker rod bearing? This really should need more than 5 thou machined off to be smooth again, is that enough tolerance for even a stock bearing?

Long story short, what's the limits for machining on the right side case to fit stock crankshaft bearings, and if oversized bearings exist how big is too big?
 

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Discussion Starter · #3 ·
Ope, I mean crank bearing not rod bearing for the oversizing, thankfully the only damage I've found to this engine would be that crank bearing riding in the right side case.

The "manual" that states tolerances and such, is that the infamous one that's referenced in this forum for free download all the time, or is this a different one?
 

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Discussion Starter · #6 ·
but why it happened will need to be sorted out. Good luck.

Yeah, I'm still looking into that, the OD of bearing is definitely worn and pitted, with some gouging on the case, but the crank itself is visibly flawless, I doubt it's out of round, but I'll be sure to check.

I'm 100% the kind of person who likes to try anything once, so I might push my luck with repairing the current case, I do have a 3d printer, and am entirely too familiar with using a set of micrometers, so I'm not too worried about getting measurements right, my biggest worry would be the process of filling in the negative space currently on the case, I'm rather proficient with Flux core welding, but not with aluminum welding, so I'd have to outsource that labor.

Regardless, thank you all for your information and input! I'm shopping for cases at the moment, and it seems that that will be my best option, financially and labor wise.
 

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Discussion Starter · #8 ·
I have been having some oil pump cavitation issues with this engine for a while, it seems to scoop air somehow and needs the oil filter bleed trick every now and again, and I would frequently (I know I'm a horrible rider for this 😅) cold start it <60⁰ and ride immediately, it wasn't uncommon for the bike to throw the oil light when stopping at a traffic light less than a mile from my starting location, but when riding light was off. So I know it's had oiling issues, I'm definitely going to be deeeeeppp cleaning all the oil passages I can, cleaning the case like crazy, and checking the pump and whatnot. This engine does seem tk have either had new internal oil tubes, or repairs to these tubes as they appear to be significantly more copper in color than the stock ones I've seen, and the silver(?) welding material used on the tabs is distinctly visible despite an other wise dirty and oily case. The case does show signs of a previous rebuild. So I wouldn't be surprised if a previous owner of this engine had oiling issues and also damaged the crank bearing.

But as far as my crank goes, absolutely no discoloration, fading, fogginess, scratching, scoring, etc. Crank looks good, and the ID of the crank bearing looks good, natural wear, but good. As I was splitting the case, the bearing popped out with the crank, so it sounds like the case may have been previously damaged.
 

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Discussion Starter · #11 ·
I bit late on the replies here sorry yall, had some hefty load bearing member relocation happening in my house.

I would normally use valvoline high mileage full synthetic automotive oil, shortly before adopting this issue I switched to a motorcycle specific oil sold at my local oreilleys, the name and brand eludes me at the time being.

Spockster, it seems you've confirmed my fears, that I was more likely than not the reason why I had oil "cavitation" issues, and consequently a damaged bearing.

Once I finally get this thing rebuilt, I will undoubtedly be better at actually letting her get up to temp before riding 😅

I appreciate you all giving such input, I'm definitely going to be buying new(used) case half/ves to remedy the damage I've caused, and will check all the oiling passages and tubes for leaks and damage before final assembly.
 
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