Engine rattle whilst cold

flipper · Post by **flipper** » Tue Apr 09, 2013 5:06 am

Bit of a saga with this, but hopefully someone will read the whole lot and be able to provide a solution!

First, the history - it is a 59X 1988 TT600, but the same engine as all the other XT/TT Yamhas of that vintage used.

I bought the bike about 6 months ago with the aim of making a nice reliable bike to use for desert rides in central Australia. It has only 3500km on the speedo.

When I first cranked it up, the engine rattled like it was about to explode. I shut it down immediately!

The bike had been rebuilt prior to my purchase with a Wiseco piston and ring kit. The bore still has hone marks on it. The guy that bought it prior to me rode it once and decided it was too rattley to be safe, and parked it.

When I got it home, I found that the camchain guide on the front of the engine was inserted wrong - the bottom seat was missed, and the guide was positioned incorrectly (I have photos if needed). Both camchain runners looked to be in perfect nick, so I simply reseated the front guide into the correct position and put the engine back together. I did replace the camchain with a genuine Yamaha one, as I figured the original one may have been stretched a bit if the bike was run like it was.

As mentioned earlier, the piston and rings were new - Wiseco rather than OEM, but I won't hold that against them.

All new OEM gaskets were used in my rebuild. The rockers were adjusted to spec (were already right anyway), and the oil and filter refreshed.

Now to the problem:

At startup, and EVERY cold startup afterwards, the engine starts to rattle from the top end after about 15 seconds. It is like the oil feed has failed.
The noise goes away after about 5 minutes, when the bike is properly warm.

If the choke is left on to make it rev a bit higher, then the noise goes away immediately, but if I turn the choke off, it immediately returns with the lower revs that come with no choke.

Whilst it was still cold ( but running), I checked the oil bleed screw on the filter housing, and it was spurting everywhere.

Regardless, I changed the oil pump to a new later model OEM one with a higher volume, but no change. Every seal on the cases have also been changed, as well as the check valve and spring.

So, I'm at my wits end. The bike runs perfectly once warmed up. but I grit my teeth every time I start it from cold! The piston clearance is fine BTW.

Can anyone offer a suggestion on this?

flipper · Post by **flipper** » Tue Apr 09, 2013 5:18 am

Just to add to this - I had a TT600 in 1983, so I am comfortable that I know what sounds correct when running these engines.

Eric66 · Post by **Eric66** » Tue Apr 09, 2013 5:28 am

Hey Flipper, I have rebuilt 2 motor's completely for my Tenere's, the 1st one has a knock but goes well ( I put it down to a bit of looseness in the crank bearings) the 2nd is real quiet and I only realized the knock in the 1st one after riding the quiet 2nd one.Mine knocks cold or hot, maybe your bike has been bored out just a little too much for the piston, wiseco recommend 5 thou clearance, could be taking a while for the forged piston to warm up and expand a little???
Regards Eric

flipper · Post by **flipper** » Tue Apr 09, 2013 5:39 am

Yes, it MAY be a forged piston warming issue, but to me, it doens't sound like it.

I've run many forged pistons in the past, and none of them have taken 5 minutes to warm up and relieve the rattle - more like 20 seconds.
When the choke is on and the revs are above 2k, the engine sounds fine. If it was a piston clearence issue, then I would expect it to worse rather than going away...

The big-end clearence is fine, as I would expect from a TT with less than 4k on the clock.

And I'm not trying to detract from your reply - I thank you for making suggestions!

Tommy10bikes · Post by **Tommy10bikes** » Tue Apr 09, 2013 6:23 am

Hi , I have 2 59x ' s and one of them knocks which i put down to little end bearing noise, i know this
as i have just rebuilt my TT600R which had the same problem. The 59x has a nickersil bore so if its
on it original bore could be piston slap, little end play is a continuous knocking from the barrel area,
it doesnt need much play in the little end either to make a racket.
You need to check for ovality in the little end but they should sound smooth engine.

Not 100%sure on this one but the engine isnt wet sumping leaving no oil in the feed tank
to feed the oil pump oil pump, like is say just a though so dont shoot me down.

TTB

GeoffD · Post by **GeoffD** » Tue Apr 09, 2013 9:03 am

I bought a brand new XT600 in 1985, it did exactly the same as yours from the day I got it :-/ it was thrashed on & off road until 1994 when I sold it with 30 thousand miles on it... It never missed a beat. I did take it back to the shop complaining about the knock but they said it was 'normal' ... I also bought a new 3AJ in 1988 which didn't knock & none of my current bikes do it so I dunno mate :-/

GeoffD · Post by **GeoffD** » Tue Apr 09, 2013 9:12 am

But I also thought it was an issue with the oil pressure/oil pump & I reckoned if something went wrong it would be fixed under warranty by the shop... Nothing went wrong

flipper · Post by **flipper** » Tue Apr 09, 2013 9:50 am

I would never shoot down someone who takes the time to make a reply to my query. Thank-you to anyone that has a suggestion that might help to point me in the right direction!

The little end is a possibility, but I would have expected it to remain noisy at 2k+ whilst cold, and at idle once the engine is warm. In my case the engine sounds fine with the choke on (when cold), and it idles happily without any noise when warmed up. I did check the bearing play in both the small end and big end when I had the engine apart, and could not see any issue.

Having previously had a 600, I would NOT consider this to be a normal noise.

I'm not talking a little rattle either - picture the top end without any lubrication, and you will understand why I'm trying to sort this out!
Once the bike is warm (5 mins plus), the noise goes away completely.

Regards,
Peter

ActionManMelb · Post by **ActionManMelb** » Tue Apr 09, 2013 10:19 am

A common source of loud and potentially fatal noises is the nuts on the end of the crank and balance shafts coming loose and flogging out the key-way.
If the key-way shears, the resulting collision between the crank and balance shaft will smash the engine cases.

Ask me how i know!!

Before you ask, yes, in the initial stages the noise can be temperature dependent.
You must remove the clutch cover to inspect.

flipper · Post by **flipper** » Tue Apr 09, 2013 11:03 am

Yes, I've dealt with the loose nut scenerio in the past - my last TT was kitted out to 640cc, and suffered all the issues that seem to go with over stressing these engines. This one is stock both in capacity and compression, just with a Wiseco piston fitted!

I checked the clutch, crank and balance shafts just a couple of days ago when I put the new oil pump on - nothing was loose. Wish it was that simple!!! Keyway on the crank is fine too, and I actually turned the woodruff key 90 degrees (even though it looked fine)to ensure that wasn't the problem!