Author Topic: Yoshi rods bearing problem (Read 2792 times)

teebee67 · « **on:** June 07, 2018, 02:28:16 pm »

I bought an engine from the States which was built in the early 70's with Yoshimura parts (crank done by Yoshi, Yoshi rods, pistons, head, cam etc). The engine had never been run. I have run the engine up several times and done a few steady laps of my local race circuit. No knocks or rattles, good oil pressure, no smoke, etc. I have now stripped the engine and found the 2 offside rods have a lot of up and down play in them. I split the rods and the bearings appear to be brown or black and marked DSK - A STD but they are not dark coloured with no central hole like the ones pictured at Cycle X and David Silver spares, they are more like mains bearings - shiny white coloured with a central hole (which is required as the Yoshi rods have a central location peg in the big end cap ( they don't have the groove that the mains shells have). I have now plistigauged one of the rods and it is about .003" which I think is the service limit. The Yoshi rods have no markings as per Honda rods and I am not 100% sure of the colour of the shells so I have no clue as to what I can do. Any help/ideas greatly appreciated.

MRieck · « **Reply #1 on:** June 07, 2018, 06:19:39 pm »

Generally aluminum rods have minimum big end ID's. Black or brown bearing would be very tight unless the journal is very very small (which I doubt). The 3 sets of Golden Rod I just mounted all used yellow bearings.
The con rod bearings have to be drilled for the locating dowel.

teebee67 · « **Reply #2 on:** June 08, 2018, 01:25:16 am »

Thanks for the reply. Are you saying the purchaser has to drill the shells for the locating dowel ? Not sure I could do that accurately enough. The journal (measured with an ordinary micrometer rather than one that goes down to tenths of thous) would seem to be towards the top end of spec (I will check it again today).

MRieck · « **Reply #3 on:** June 08, 2018, 05:51:40 am »

Quote from: teebee67 on June 08, 2018, 01:25:16 am

Thanks for the reply. Are you saying the purchaser has to drill the shells for the locating dowel ? Not sure I could do that accurately enough. The journal (measured with an ordinary micrometer rather than one that goes down to tenths of thous) would seem to be towards the top end of spec (I will check it again today).

Yes....they have to be drilled. I have a jig to do that accurately. And yes.....I am not surprised the journal is towards the the large end of the spectrum....that's the way it usually goes.

Bill/BentON Racing · « **Reply #4 on:** June 11, 2018, 03:34:07 am »

+1

teebee67 · « **Reply #5 on:** June 11, 2018, 11:46:10 am »

If I'm reading my workshop manual correctly I think black shells are the thickest going down to yellow being the thinnest. Can anyone confirm this (or correct me) please?

Cb750 Racer · « **Reply #6 on:** June 11, 2018, 02:36:35 pm »

Quote from: teebee67 on June 11, 2018, 11:46:10 am

If I'm reading my workshop manual correctly I think black shells are the thickest going down to yellow being the thinnest. Can anyone confirm this (or correct me) please?

Correct. The order is:

Black (Thickest)
Brown
Green
Yellow(Thinnest)

Big Jay · « **Reply #7 on:** June 14, 2018, 02:34:08 pm »

Back in the day when we were installing aluminum rods in the Hondas, we just took a stock rod cap, centered it up in the mill and drilled a hole on it. That was our bearing drill jig.

teebee67 · « **Reply #8 on:** June 14, 2018, 11:58:00 pm »

I haven't got a mill or even a lathe now so I guess it's a job I will have to farm out. My main concern is that, although these rods are unused, they seem to have black bearings fitted and still have excessive clearance - not sure what I can do?

PeWe · « **Reply #9 on:** June 15, 2018, 02:56:30 am »

APE can provide fresh rods!

MRieck · « **Reply #10 on:** June 15, 2018, 04:47:10 am »

Quote from: Big Jay on June 14, 2018, 02:34:08 pm

Back in the day when we were installing aluminum rods in the Hondas, we just took a stock rod cap, centered it up in the mill and drilled a hole on it. That was our bearing drill jig.

Exactly

MRieck · « **Reply #11 on:** June 15, 2018, 04:49:05 am »

Quote from: teebee67 on June 14, 2018, 11:58:00 pm

I haven't got a mill or even a lathe now so I guess it's a job I will have to farm out. My main concern is that, although these rods are unused, they seem to have black bearings fitted and still have excessive clearance - not sure what I can do?

That's odd.....something not right there

teebee67 · « **Reply #12 on:** June 15, 2018, 04:54:46 am »

PeWe I know that but I spent a small fortune buying a full Yoshi motor that had never been run and now I'm needing new rods. I do have 3 Cycle X Super rods that have only done about 50 miles so I have ordered a rod from them.

teebee67 · « **Reply #13 on:** June 15, 2018, 04:56:57 am »

Quote from: MRieck on June 15, 2018, 04:49:05 am

Quote from: teebee67 on June 14, 2018, 11:58:00 pm
I haven't got a mill or even a lathe now so I guess it's a job I will have to farm out. My main concern is that, although these rods are unused, they seem to have black bearings fitted and still have excessive clearance - not sure what I can do?
That's odd.....something not right there

Yes you're right. I am not sure that they are black as the engine has been run but I think I can just about see a little black (or possibly brown) on the edge of one of the shells.

MRieck · « **Reply #14 on:** June 15, 2018, 01:55:25 pm »

Can you pull a rod, disassemble and measure bearing thickness? Or do a quick and dirty measurement of the big end ID with some verniers (with bolts torqued to spec and measurements taken at different spots).

Big Jay · « **Reply #15 on:** June 15, 2018, 03:43:58 pm »

You can send us the aluminum rods and we will measure them for you.

teebee67 · « **Reply #16 on:** June 16, 2018, 05:06:43 am »

I can measure the bearing thickness and the rod diameter but I only have standard micrometer and vernier (I am told they are not accurate enough). Thanks Big Jay but I am in the UK so perhaps not practical to send the rods to you (time is very tight for me now) but thanks for the kind offer. Perhaps I need to invest in some more accurate instruments.

teebee67 · « **Reply #17 on:** June 18, 2018, 02:28:44 am »

Hi again,
Does anybody know where I can get the correct rod bolts for the Yoshi rods.

MRieck · « **Reply #18 on:** June 18, 2018, 03:37:46 am »

Quote from: teebee67 on June 18, 2018, 02:28:44 am

Hi again,
Does anybody know where I can get the correct rod bolts for the Yoshi rods.

Maybe ARP. What is the length and pitch?

Big Jay · « **Reply #19 on:** June 18, 2018, 02:59:44 pm »

I see. We have a master gauge 1.5360" for setting the dial bore gauge.

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Author Topic: Yoshi rods bearing problem (Read 2792 times)