G16-29 undersize Conrod Availability?

Rob_C · 05-20-2021, 11:39 PM

Evening viewers,

Had a customer not check the oil in their cart since moses played football for Jerusalem, with the predictable results. Oil was added and it started and ran with a knock so they kept using it until it "went CLUNK and when we tried to start it the belt kept slipping, can you just adjust the belt"? Their words not mine.

When I opened it up, both rod bolts had snapped, the slinger was broken off the rod and the cap was laying in the bottom along with a large amount of previously essential metals. Surprisingly the bores fine and the piston has only slightly picked up on the lands so I assume only the big end siezed.

Anyhow, to get to the point, everything is reuseable but I believe the crank journal will need a grind (I am yet to linish and measure it. I can not find a listing anywhere for an undersize Yamaha connecting rod, are such animals available or am I looking for a new crank?

I'll throw some images on later for your education and amusement.

Cheers,
Rob

Cartmaster · 05-21-2021, 01:49 AM

If it is anything like the Ezgo robin engines, linishing the crank is usually sufficient to rebuild as stock. Assuming the Rod is aluminum cleaning the crank is easy as it does not usually damage the crank.

Rob_C · 05-21-2021, 04:02 AM

Thanks Cartmaster,

I'm hoping that's the way it will work but it doesn't hurt to be informed up front. The rod is alloy riding directly on the crank.

At the moment the journal looks atrocious but I'll give it a linish and measure up in the morning. They want $A795 for a crank here so it'd be quite a saving for the customer too.

Cheers,
Rob

Cartmaster · 05-21-2021, 04:56 AM

i would definitely give it a go, If you fitted a new crank, do you really think they would check the oil in the future?

And yes, pictures for the masses would be a good lesson LOL

rstacy · 05-21-2021, 06:09 AM

I have seen this a handful of times. I have never lost a crank. They clean up well with fine emery cloth and scotch brite pads. Its amazing to see what a Yamaha engine can take.

crash12888 · 05-21-2021, 06:39 AM

I agree with the masses, usually even a first glance ugly journal is just aluminum stuck to it. Polish and mic it and all should be good.
Check the low oil alert system for a bad bulb?

Edit: And charge him anyway, make it sting a little bit he might remember to check the oil.......

Rob_C · 05-21-2021, 06:40 PM

Thanks you Brains Trust,

I'll clean it up and check it this morning.

The customer is actually a local 9 hole golf course, it's their range cart so it's not like they need it daily.

I rebuilt the engine maybe 2 years back, 6 months later, someone had not fitted the air flilter top correctly and dusted it down. It was smoking like your neighbours worst BBQ.

I told them it was another rebuild so they elected to live with the smoke which was somewhat less if oil was only filled to just over the add line. A month later it wasn't smoking any more, I double checked the oil and can only assume the rings had enough tension to reseat.

The supervisor for last Saturday pulled the dipstick, it had oil on it so sent it out. Not sure how many times I have told each of them to wipe it and dip it for a true reading. Sunday it went bang, Wednesday the rang me, I picked it up Thursday afternoon, disassembled yesterday and they rang me last night to see when it would be ready

Film at 11...

Cheers,
Rob

Rob_C · 05-21-2021, 07:09 PM

Pics as promised, the usual detris in the air intake and jammed in the fins under the plastic shroud that in summer here would have killed the oil ring and made it a smoker. Stick your hand in there and clear it regularly, especially if it's in autumn.

Rob_C · 05-21-2021, 07:11 PM

Sorry about the "soft" focus on the rod, the camera just refused to focus on it.

Rob_C · 05-21-2021, 11:11 PM

Yamahas specs for the crankshaft big end journal are doing my head in.

Min 35.97mm (1.4161")
Max 35.98mm (1.4165")

BUT.. the out of round or taper limit is 0.03mm (0.0012")..... so max either end of the scale puts you well out of spec.

Same goes for the oil clearances on the rod.

0.016mm-0.046mm
0.0006"-0.0018"

Limit 0.1mm or 0.004"

Is the factory manual scewed up? These seem incredibly tight tolerances on the rod.

05-20-2021, 11:39 PM	#1
Rob_C Getting Wild Join Date: Dec 2017 Location: Richmond, NSW Australia Posts: 115	G16-29 undersize Conrod Availability? Evening viewers, Had a customer not check the oil in their cart since moses played football for Jerusalem, with the predictable results. Oil was added and it started and ran with a knock so they kept using it until it "went CLUNK and when we tried to start it the belt kept slipping, can you just adjust the belt"? Their words not mine. When I opened it up, both rod bolts had snapped, the slinger was broken off the rod and the cap was laying in the bottom along with a large amount of previously essential metals. Surprisingly the bores fine and the piston has only slightly picked up on the lands so I assume only the big end siezed. Anyhow, to get to the point, everything is reuseable but I believe the crank journal will need a grind (I am yet to linish and measure it. I can not find a listing anywhere for an undersize Yamaha connecting rod, are such animals available or am I looking for a new crank? I'll throw some images on later for your education and amusement. Cheers, Rob

05-21-2021, 01:49 AM	#2
Cartmaster British born Nincompoop Join Date: Feb 2007 Location: United Kingdom Posts: 2,463	Re: G16-29 undersize Conrod Availability? If it is anything like the Ezgo robin engines, linishing the crank is usually sufficient to rebuild as stock. Assuming the Rod is aluminum cleaning the crank is easy as it does not usually damage the crank.

05-21-2021, 04:02 AM	#3
Rob_C Getting Wild Join Date: Dec 2017 Location: Richmond, NSW Australia Posts: 115	Re: G16-29 undersize Conrod Availability? Thanks Cartmaster, I'm hoping that's the way it will work but it doesn't hurt to be informed up front. The rod is alloy riding directly on the crank. At the moment the journal looks atrocious but I'll give it a linish and measure up in the morning. They want $A795 for a crank here so it'd be quite a saving for the customer too. Cheers, Rob

05-21-2021, 04:56 AM	#4
Cartmaster British born Nincompoop Join Date: Feb 2007 Location: United Kingdom Posts: 2,463	Re: G16-29 undersize Conrod Availability? i would definitely give it a go, If you fitted a new crank, do you really think they would check the oil in the future? And yes, pictures for the masses would be a good lesson LOL

05-21-2021, 06:09 AM	#5
rstacy Gone Wild Join Date: Nov 2013 Location: Western NY Posts: 644	Re: G16-29 undersize Conrod Availability? I have seen this a handful of times. I have never lost a crank. They clean up well with fine emery cloth and scotch brite pads. Its amazing to see what a Yamaha engine can take.

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05-21-2021, 06:39 AM	#6
crash12888 Gone Crazy Join Date: Jan 2007 Location: Chesterfield, Va Posts: 6,021	Re: G16-29 undersize Conrod Availability? I agree with the masses, usually even a first glance ugly journal is just aluminum stuck to it. Polish and mic it and all should be good. Check the low oil alert system for a bad bulb? Edit: And charge him anyway, make it sting a little bit he might remember to check the oil.......

05-21-2021, 06:40 PM	#7
Rob_C Getting Wild Join Date: Dec 2017 Location: Richmond, NSW Australia Posts: 115	Re: G16-29 undersize Conrod Availability? Thanks you Brains Trust, I'll clean it up and check it this morning. The customer is actually a local 9 hole golf course, it's their range cart so it's not like they need it daily. I rebuilt the engine maybe 2 years back, 6 months later, someone had not fitted the air flilter top correctly and dusted it down. It was smoking like your neighbours worst BBQ. I told them it was another rebuild so they elected to live with the smoke which was somewhat less if oil was only filled to just over the add line. A month later it wasn't smoking any more, I double checked the oil and can only assume the rings had enough tension to reseat. The supervisor for last Saturday pulled the dipstick, it had oil on it so sent it out. Not sure how many times I have told each of them to wipe it and dip it for a true reading. Sunday it went bang, Wednesday the rang me, I picked it up Thursday afternoon, disassembled yesterday and they rang me last night to see when it would be ready Film at 11... Cheers, Rob

05-21-2021, 11:11 PM	#10
Rob_C Getting Wild Join Date: Dec 2017 Location: Richmond, NSW Australia Posts: 115	Re: G16-29 undersize Conrod Availability? Yamahas specs for the crankshaft big end journal are doing my head in. Min 35.97mm (1.4161") Max 35.98mm (1.4165") BUT.. the out of round or taper limit is 0.03mm (0.0012")..... so max either end of the scale puts you well out of spec. Same goes for the oil clearances on the rod. 0.016mm-0.046mm 0.0006"-0.0018" Limit 0.1mm or 0.004" Is the factory manual scewed up? These seem incredibly tight tolerances on the rod.