One more top end rebuild

[Capau]

Hi there, TRX fans.
Greetings from cold and snowy Moscow, Russia.
I spent a lot of time lurking through the forum, so I understand the whole picture of the topic name (and besides it's not my first engine rebuild, and not second), but I still have some questions.

First of all the situation I got into:
I purchased this TRX'96 during winter, so couldn't test ride it, but it showed a good cold start, nice sound of the engine, and previous owner was honest and informed me about 100-300ml oil consumption per 1000km. Also it has 43000 on the clock (which sounds true, because original drive chain and drive sprockets are still in). The only thing I really didn't enjoy is the fact that nobody is known to check valve clearances.
No big deal, I took it to the shop, disassembled the cam cover and found nearly zero lash on intake. My experience, google search, and your forum told me that the only right way is to replace the valves. I also had a present from a previous owner with head gasket, valve seals, piston rings and some minor rubber parts. So a replacement of the rings sounds a good idea.

And now the questions themselves:

1. Valve question: I replace the valves, if seats in the head show no damage i just lap the new valves. Is that end of story for this?

2. Barrel question. Here is something I'm not familiar with. The glazing which appears to be a well-known problem for TRX engines. What does it look like, could it be seen? I've measured the barrels and they show nothing critical, 89,51-89,52. The surface looks like the pics in this thread http://www.trx850.com/phpBB_forum/viewt ... ing#p55817. I'm going to make some pics on Monday, but it won't be a lot different.
Is that mirror-like part in the center glazing itself? I can see honing through the mirror shine.
Is it the thing I should fight with? Do hone or even sandpaper solve the problem?

3. Break in after repair. No gentle breaking in. A good load from the very beginning through 50km or so, than 1000km oil change and then just common riding. Is that correct?

[cobbadiggabuddyblooo]

Replace inlet valves and lap all valves including exhaust.
The rubber things sounds like the 10 valve guide seals.
Replace these too.
Use plenty of assembley grease on the cams and prime all the oil galleries and top end oil feed pipe by pushing oil into them with a syringe.
DO NOT OVERTIGHTEN THE CAM CAPS ... 10Nm is Yamaha spec.
There is a workshop manual you can download from the " download section " of the forum.
It will also explain about the oil feed bleed/inspection bolt on the end of the exhaust cam oil galley.
The inlet cam on No-2 cylinder gets starved for oil on initial start up after a rebuild so that's why it's best to get as much oil and lubricant to minimise this.


Plateau hone the bore and load the motor when running in. Lots of short bursts in 3rd 4th and top gear from 2500rpm with lots of throttle to get the rings to bite and bed themselves for The first 10-15 minutes.
You will need a new base gasket and 2 big o rings on the bottom of the barrels , head gasket , 10 valve guide seals and cam cover gasket. Quite often you can re use the cam cover gasket a number of times.
Place a small amount of gasket goo / Yam bond or similar at 50-75mm intervals on the cam cover to help locate and hold the rubber gasket on the cover.
Next time you need to remove the cam cover the gasket will seperate easily from the head and stay in place on the cam cover and make it easy to locate and bolt the cam cover back on when finished.

[Capau]

Thanks a lot.
All new gaskets and O-rings - check.
Service manual (even two of them) - check
Torque wrenches - check

I thought about placing the second bleed bolt in the intake cam gallery(lurked through your topic already), worth it?
Maybe I could use these bleed bolts to fill the head with oil after assembly?

Once more thanks.

[cobbadiggabuddyblooo]

As a final note... If you can stick with genuine OEM yamaha gaskets for the head/base gaskets...
If you have a little extra in your budjet, place a cam chain in it too.

[Capau]

It's a pleasure when two people, who know something about engines have a conversation.

OEM gaskets - check
New cam chain - check

An it's not much about budjet. I'm not a rich man, but even more than saving money I want to do this repair ONCE, not more.

Did you do an extra bleed bolt for intake gallery? What's the order of oil bleeding than? Turn both out, then plug in order the oil comes out. I suspect that there isn't much flow there due to orifices in banjo bolts in oil feed tube.

[Trixed]

I am doing a top end rebuild too currently and am getting an inlet bleed screw threaded to add a bolt same as the exhaust.
Have a small scouring on that bush. Also have another head that is has a lot more damage and I can see how it can go wrong.
Valves are expensive too and ten of them!

[Capau]

So let it be the bleed bolt for intake. It's never too late to make an old bike better. Thanks for your reply, I was in doubt before, but not any more!

I went with replacing just intake valves, as they seem to be a problem. Found nothing wrong with either exhaust backlash or the valves themselves.

[Capau]

Hi again.
As the engine is allready assembled there is time for a first ride. Besides all the internal engine stuff there was a Factory Pro needle and jet kit installed. And it's the point where new questions arose.

First of all please take a look at the pic. On the right there is the sketch of an original jet needle setup. It has a clip, a thin steel washer below and a thick plastic washer under.
I assembled FactoryPro parts in this order and found out that I cannot achive a normal operation in any clip position. At groove 5 the engine was bogging at ~5k rpm, at groove 1 it was bogging at 7,5k. After that I put the clip in groove 1, removed the thin steel washers (whitch were 0,5mm thick) and achieved more or less normal operation.

Then I noticed, that if I remove both steel and plastic washer and put clip in groove 3 (the middle one) I achieve the same position of the needle as with groove 1 clip and plastic washer in. So I removed both steel and plastic washers and result was even better. The engine finally gave really good power.
By the way I mentioned there is a step inside throttle slide (see pic on the left). The size of the step allows the clip to pass it, going to the bottom of the slide. But when plastic washer is in, it lays on a step, so the needle itself is angled towards intake. Hope you can understand me.

Finally the question. The engine works fine, but it seems strange to me that I had to rework all the things in such a way. Did I do something wrong, or is it kind of a standard procedure with FactoryPro kit?

[dandywarhol]

From memory, one of the washers thickness gives you the option of having the needle position between the grooves in the needle for a fine tuning

[Capau]

Got it.

But how comes that I need to remove the plastic one to make carbs work fine? Is it a sighn of misassembly of the whole carb? And do I really need that angle of a needle?

[cobbadiggabuddyblooo]

Compare the overall length and the bottom taper angle of the factory pro needle to the Std needle and you may find your answer.

[Capau]

Thanks.
I'm going to do it on saturday, I'm away from the bike now. Just thought someone has allready come across this situation.

[dandywarhol]

I never got Factory Pro needles to work well at small throttle openings due to the steep taper. I resorted to using stock needles with FP emulsion tubes

[Rod.s]

factory pro, developed their kit using the only bike that had in 1992/93, a 360deg, 850TDM. With different engine characteristics/cam etc these kits will always be at best, marginal. Also be aware that they use the same material for both the tubes and the needles which over time will wear the needle badly, this is due to electrochemical corrosion (galvanic corrosion). I've seen needles with less that 10000K's completely corroded through in one place.

[Capau]

So, after days of experiments, I'm almost desperate. The bike is running rich. At any clip position. If I twist throttle wide open it starts to "doo-doo-doo" and no acceleration. The worst is at 4000, but it gives me a punch at any rpm. And it runs approximately 180km on full tank. The only thing that helpes is to remove the filter box. Then it runs well and pulls hard.
I've done:
- fuel level from 12 to 15
- all clip positions
- blocked the choke system with pieces of o-ring. Had run well 100km aftre that. Then after 7 hours on a parking the problem returned.
- blocked the acceleration pump (I've got a Japaniese TRX) the same way
- cleaned carbs 3 times.

Would appreciate any help. I'm about to burn the thing and dance on ashes.