Con rod meets cylinder - advice needed

[Paulrs]

I will post a photo tonight. You are correct the fat bit is the bit above the machined area.

I had briefly considered "smoothing" the rod, and will have another look at it tonight as it would do the job!

If I have to strip the engine to do the mod, I would rather send the crank back instead.

Paul

[andy]

Damn, wish I had saw this before purchasing two pairs of these hunks of junk from Gus. Building two engines for customers, one stock (with OEM Yamaha pistons) and one performance engine. Luckily I always spin each crank before installing drive gears and clutch. BOTH engines suffer the same thing. The upper left will not make a full rotation. Viewing through the intake with reeds out reveals the big end contacting the upper case at the "shelf". I have emailed Gus about this weeks ago. He has fallen off the planet. I now must disassemble both engines, machine a clearance in that shelf, re-clean cases, reassemble..........and send Gus the bill. Or I add it onto the invoice and a pair of irate people will be seeking Gus out. Exorcise caution if you purchased a set of these heaps. Do a dry run first. Install cranks, snug up cases, install/snug top end, test for rotation before wasting seals, gaskets, pulling a set of sealed cases apart......again.

[silverstrom]

Now I'm wondering about my cranks from Gus. They are still in the box and have not been tested yet. FFS...I'll have to put them in cases and check them.

I did try multiple times to get specs from Gus before buying mine, but it was an impossible task. I know that Yambits had issues with some of the RZ500 rods they were selling not long ago. Same interference issue. I asked Yambits about it and they told me the rods are made in Taiwan and they had removed the defective rods from their supply chain. I'm certain Gus's cranks are coming from Taiwan and it seems they have not eliminated the oversized big end issue.

The crank is a precision assembly and this problem should not be happening. If they can't get the simple things right, why should I feel 100% confident in the rest of the assembly?

Is it safe to assume that all crankcases are precision made to an exacting standard and there is no deviation between case sets? That leaves incorrectly manufactured rods as the only possible answer?

[AndyT]

Just had the same issue while reassembling my engine. Got my cranks from driveline performance. Top left rod hitting the the top case when the crank is rotated.

Took the engine apart again and relieved the area on the case where the rod was contacting. Checked the rods with the old crank rods and yes the drivline rods are fatter at the base of the rod.

[Speed Freak]

When I go to the garage this weekend I will take the disassembled crankshaft with me, then I can scan a Yamaha and one Yambits conrod.

Let's see what's the difference.

Before someone throws this cranks into the junk let me know.

[Ron57]

Hi, gus's rods are bigger, weight difference on the cranks is only a few grams.

[lost1750GTV]

He should have a mailer to all customers, not everyone is on social media.
I think if I'd seen this thread before buying recently - I probably still would have. But considering this goes back 4 years, he should have known and informed past and potential customers.

[Speed Freak]

I think this picture shows quite clear what`s the issue (yellow = Yamaha, green = Yambits):


Second big difference is that the lubrication cut is more narrow on the Yambits conrod and the machining on the inside is different.
The Yambits conrod also has a bigger chamfer.
I don`t want to judge at this point if this 2 differences will make the Yamaha conrod better but at least they are a bit different in detail.

[silverstrom]

Start reading at post # 29 https://www.rzrd500.com/500phpBB3/viewt ... s&start=15

In post #34 Giron points out the rod dimension issue we are seeing again.

Post #40 Gus says there is no problem and no one has ever said there was.

This rod issue was a known issue previously. Gus denied there was a problem. Said it couldn't happen because the rods were the same as stock. Clearly that isn't true.

[RC45]

So what gets the grinder treatment? The rods or the case??

[lost1750GTV]

And there post 16 from Mr. Lance, attesting to their quality.
If/when I do mine, and if necessary, I'm leaning towards the rod getting the grinder ....

[silverstrom]

And there post 16 from Mr. Lance, attesting to their quality.
If/when I do mine, and if necessary, I'm leaning towards the rod getting the grinder ....

They're fine....when they fit. Not all have had the big end interference issue, apparently. The positive reviews are obviously for cranks without issues. For anyone thinking of buying them, how lucky do you feel?

I still haven't checked mine.

[busa1300]

After reading the concerns about where they were made and what bearing manufacturer was being used, as well as material used for the crank itself.....I'm glad I spent the $$$ to rebuild my genuine cranks instead...

[tacky1]

I got lucky. I bought 4 sets. Used 3 with no problems. I might pull down the 4th set and check them.

[Luther]

I built my cranks with Yamaha parts and finished about a month before Gus offered his first batch. While I was partially assembling things and measuring I put cranks, pistons and cylinders in top case upside down on bench. The stock rod was too close to the case while spinning them around so I used a rat tail file and took a couple mm off case in the one spot its close. The paint on case was nicked where a stock rod had been touching. Its the corner under exhaust where the round area meets the vertical. The choice is do I grind a rod in a critical structural area or remove a little aluminum from where it shouldn't be.