Ya name brands are what I'm referring to . Things made by Chinese or those outsourced I couldn't say are better . The technology in manufacturing the races and especially ball bearings is what better . The balls are a more true sphere and hold less piece to piece variances not to mention metallurgy more refined . I wouldn't even consider a Chinese bearing for the crank , even if it had the correct class spec .

In reality the C3's may run better/smoother/quieter , they usually do in many situations , but also may not in this spot . I would think the reasons I said are likely why they went with the looser ones . I know at work it doesn't take much to make a bearing run hard , just .0003" extra press can make one drag and feel rough .

So I spoke to David, I could actually call him directly! Very nice of him.

So conclusion:
- C3 bearings are fine, aftermarket good quality ones too, he recommends koyo
- The bearing on the crank is actually a floating bearing! When the crank heats up, the bearing can move. Therefore it doesn't really matter where the bearings sits. It's the position the bearing was in the last time the engine cooled down. The position of the timing/chain gear is more important - and this one is fixed. It's important to measure where it sits before replacing the bearing.

- The output transmission bearing on the left side is a special bearing, and might need to be yamaha OEM.

- He recommends 10W50 over 10w40

- The 3aj gearbox gears / design is still crap. He said it's pretty much a waste of money to rebuild the entire engine without replacing the gears/transmission for aftermarket/newer parts, since the pitting (and as a result lose chunks) will wear the engine again anyway.

Anyway there was another thing regarding this engine, and that is the fact that there's 0.9mm sideways clearance on the big-end. (manual says 0.35-0.65mm). Vertical play is 0, so that's good.
Also, the crank width itself it 75.25mm instead of 74.95-75.00.

My idea was to have it re-pressed -0.30mm so both are within clearance again. However I just came back from the shop and it might be 90euros and he won't have time until 2 weeks.
With the above and the gearing thing, I'm now thinking about just leaving everything as it is (I bought this bike non-running) and see what's what. (with thicker 50 oil)
Will save me lots of euros.....
I'm not sure what the end-goal here is that's the problem. If I want to travel long distances on it in the future it might be worth it.
:wacko:

Yeah, SKF and many others have factories in China.

So did some better inspection on my gears. The output shaft looks fine visually, no pitting to be seen with naked eye.
The input shaft has some pitting on the 4th and 5th gears, on some of the teeth (i'd say on 1/4 of the teeth). These are the worst ones. 3rd gear has slight dents on 2 teeth also seen on the photo.

https://www.dropbox.com/s/o6gowyc09o...5.24.jpg?raw=1

Direct link so it doesn't turn sideways: https://www.dropbox.com/s/o6gowyc09o...5.24.jpg?raw=1

Most of the other cogs on the 5th gear look fine, like the one behind the 3 pitted cogs. Looks like I got the older 3AJ gears with 19 teeth 5th gear.

Is it even worth it doing anything on this engine if I put this back into the engine? How long before this starts giving trouble? Does this gearbox still have some KMs in it without spraying chunks of metal all around the engine?

I'm assuming people replace them with XT600E gears or something? I looked at the input shaft and it seems the gears are part of the shaft so I'm guessing they need to be pulled/pressed...? Do later 3TB+ gears just swap on?

Those gears could last 5k ,8k ,12k . no way to say exactly till they start being real noisy and eventually a tooth breaks . You can only use the older gears , the E start's are thicker , though one or 2 have turned them thinner to put in the older cases , a lot of work . Other option is to find low mileage used ones that haven't started pitting or buy new , which unless the bike is in mint shape it not worth the cost IMO.


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Mine IS the E-starter by the way. New 3AJ 4th and 5th input gear is 2x80 euros. + need to be pressed on.
What about 3TB/4PT gears. They are 21 teeth 5th gear I think but do they swap in the 3AJ e-start engine?

The whole point of replacing all bearings + doing the crank + new gears is to make the engine is 'mint' condition. The barrel has been honed + new cylinder 10000KM's ago.

The alternative is to leave everything as is - old bearings, these gears and 0.9mm horizontal play on the big end. I don't want to do any of these if I'm not doing the others as well.

I guess what I'm used to is 3TB's are our e-starts , we never got a 3AJ , but it's the same as our kicker models , motor wise at least .So even though your is e-start it's still the old style and the 3TB gears won't fit as far as I remember . I rebuild 2 3tb's , one with a trashed tranny and I don't think any of the gears fit because I had several old trannie sets but still had to buy new gears for it.

Do you have a fine spline output shaft for the front drive sprocket or the course 6 spline output shaft ? That'll tell me which tranny those e-start 3AJ's used for sure, I know not all had the starter, just kick only.

As far as gearing changes , I liked the older ratios better , my 3tb has too high 1st to get a decent 60-65mph cruising rpm . I think you can put the 3TB clutch gear and primary gear on the 3AJ to get a little bit closer . It may require the input shaft changed so the clutch fits , been a few years since thinking about that and which parts do actually fit.

Quick question,

I got the full gasket set from KEDO and I'm installing the valve seals.
I noticed that one of the valve seals has an extra rubber seal/insert in off it. There other 3 were in the bag and not inside the valve seals.
With the seal in, it doesn't fit on the valve guide at all, and the original seal I have don't have it it either.

What are these seals for? The gasket set is only for 600. Is it for the old type head or something? Thanks

pic:
https://www.dropbox.com/s/c4ngz9pm8e...4.11.jpg?raw=1

XT 600 engine rebuild
 

Hi Doubleyoupee,

You may find some useful info at http://www.horizonsunlimited.com/hub...-34l-tips-5538

Cheers,
p

A lof of info there.
The conclusion is to buy 4TP gears? but they are wider?
Do they swap in 1:1 ? Or do you have to make modifications?

The best (cheapest) way for me would be only replace 5th gear on the input shaft, since the gear on the output has no visual pitting at all.

How hard is it to get the gears off of the input shaft? Can it be done with a simple bearing-pulled and heatgun?

Wear on 5th gear
 

Found this old post of what i did. You are welcome to ask questions if you need.

http://www.horizonsunlimited.com/hub...solution-80123

That modification has done 10867 km and has been completely successful.

This was about making 5th gear last. As you will see, it became about how to stop 5th gear destroying the engine.

The gears are wider. That is why they last. You will have to grind both original 2nd gears to accommodate the 3yf gears. (There is no detriment to 2nd gear, only material is taken at centre boss of small gear pressed on shaft, and a lick off the big 2nd gear)

You will need a small press. No heat please. No change to 3yf gears, fit straight in with mod to 2nd gears.

I believe the factory changed the main engine housing to fit wider gears.

Quote: "The best (cheapest) way for me would be only replace 5th gear on the input shaft, since the gear on the output has no visual pitting at all."

'Best' and 'cheapest' are not words can put together any place i know of :)

Depends what you need from the bike.

Cheers,
p

Thanks,

Unfortunately grinding things off the gears is no option for me. Too much for this project.
I wish there was just a new replacement gear that is made from a stronger material.
Too bad the kedo gears are so expensive, I'm not paying 250 euros for 2 gears....
Maybe i'll get new factory 3aj gears.. or just leave it like this..(the gears aren't THAT bad) and then just oil changes and riding carefully in 5th gear :)

Here's a NOS 4th driven gear(if it's the side needed), the same as the XT's , 34l and 3AJ should be , 1983-89 YAMAHA XT TT SRX 600 TT600 XT600 4TH GEAR WHEEL NOS OEM P/N 55U-17241-00

So after a long time I finally had time to bring the crank over to the local shop.
They pressed it but unfortunately it skipped 0.6mm in 1 go instead of 0.3mm. So now the big-end play is 0.30mm (should be 0.35mm-0.65mm) and the crank width is 74.70mm (should be 74.95-75.25mm).

They work on a lot of old engines, but mostly cars. They said 0.3mm is perfectly fine, and the 74.65mm is also fine since it has regular roller-bearings on the side.

Any thoughts? Should I go back? :huh:

That's .002" less but still .0118" clearance (SAE since I'm used to it) , it'll be ok .




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