High speed drowning

[Ubaat]

Hi guys.

I am new to the this forum and the trx850. just bought a 1996 with with ported head, rised compression, ken cams, dynojet kit, akra 2-1 titan exhaust, r1 brakes and suspension uppgrades.
It has little over 60k km on it.

My problem is that it runs to rich. At around 150-160kmh it feels like its drowning and wont go over 200kmh, and struggles to reach that. But in third gear itt will pull perfect till atleast 9500 . So the problem acures only in 4. an 5. gear
It actualey runs like a mustard cat in the 3 first gears, and no problem in 5. before 5000-6000rpm
No problems at low rpms either. But it blows black smoke when I rev it in neutral.
And its thirsty...

Anyone got any ideas?

Can it be emulsion tubes?

The work on the bike is made by a retierd Bmw road racing team mechanic. So I dont think its wrongley jetted.

Any answers would be much appreciated

Greetings from Norway

[cobbadiggabuddyblooo]

1/. How high is the compression ratio and how was it achieved ??? (Std trx piston with material removed from the head or barrels or a higher Compression forged piston and how made them??)

2/. Do you know what Kent regrind they have used???(lift and duration)

3/. Does it still use the std ignition curve???
Are they std Mikuni CV carbies with a dyno jet kit and airbox or pod filters or aftermarket carbies???
What main jet and needle position ???

With this simple information it will make it easier to find where the problem is manifesting from.

It may be an ignition timing issue due to the higher compression or possibly weak spark or it may be from the carbies.

This information will help eliminate a few options to where the problem is manifesting from..
1 simple dyno run will give you a good idea on air/fuel and torque curve and a basis to start from.

[dandywarhol]

It does sound like a fueling issue the way you describe it - you will have enough torque in the lower gears to get you through the "hole" to higher rpm but the higher gears (naturally) won't produce enough torque and you're stuck around 5/6000 rpm.
I'm assuming you're on wide open throttle (WOT) - does it try to improve if you roll off the throttle a bit, in other words, off main jet?
Due to the nature of horizontal CV carbs emulsion tubes wear oval around 15,000 kms, especially if the previous owners have used low rpm upshifts and the needles rattle the emulsion tubes oval. This tends to manifest itself as a mid throttle problem and less likely to affect WOT and the main jet.

Here's a pic of what to look for if you remove the carb tops. http://www.factorypro.com/tech/needle_jet_wear.html

[cobbadiggabuddyblooo]

There's a bit of a step up in the gear ratios from 3rd to 4th and your overlap comes into play between 4-5000 so there's usually a bit of a dip in the torque curve here so if it's a fuel issue and the load from the gearing will start to rear its ugly head.
You can usually smell the fuel when it's rich in 1st to 3rd at wide open throttle even though it revs ok while riding.

Cam duration and lift comes into play with jetting too that's why it's handy to know the set up of the carbies.
Both Yam 9 kent cams and an Akrapovic exhaust both boost your midrange so it may be as simple as smaller main jets and lifting the needle.



The std trx timing curve has a large advance from 5,000 to 6500rpm upto 37* before it dips back down to 35* so if your running over 11:1 compression this overall advance may be causing problems too.

With just over 12:1 compression I tried running over 32* at 7500 with Kent Yam9 cams and it was too much advance and it was like someone putting on the hand brake but 1st 2nd and 3rd it wasn't too noticeable but in 4th the extra load made it manifest.
This is why it's handy to know the compression ratio and hopefully this can be eliminated as a possible cause of your troubles.

If your fueling and carbies are set up right then look at spark and timing next.

[Ubaat]

Thanks guys for the replys.

I will try to get all the specs that have been done to it.

It was the first owner that did this, and I am the third. Previous owner was a sedat older guy that never had it over 140kmh or near the red line.

I have the number to the first owner. So will give him a call.

Tomorrow I will be riding to Oslo to stay with me girlfriend for a bit, and wont get time to work on it there. But when I get home I will check the carbs.

The bike also got new tires last week and got 650km on them. They are pilot power 3 with 120/70 front and 160/60 rear on standard rims. And they are great
I wanted to go 170 on the rear. But It was over 2 weeks delivery time, so I went stock on thr rear

[dandywarhol]

160 a better choice - you'll find a 120/60 front steers quicker too

[Ubaat]

Just got a little more info on whats done.

It has std trx pistons and material removed from the head. It was made to be drivable, so I dont think the compression is sky high

The receipt from kent says yam9 cams

Std carbs with dynojet kit

I think it has standard ignition, but I am physically gone check ignition box, spark plugs, and carbs when i get back home.

[cobbadiggabuddyblooo]

Your problem lies within your carbies..
Personally I would place a keyster or similar std trx Mikuni carby kit with the air box fitted and your problem should be sorted running the Std 142 main jet.
The 2 carby kits will cost a total of about $120 for the 2 ( about 90 euro ) and contains gaskets, o rings, jets, needles and emulsion tubes.

[dandywarhol]

Or better and cheaper IMO a LItek kit - won't be affected by ethanol fuels - delivered to the UK in less than a week - excellent service, quality parts and the full kit for less than 40 euros

http://litetek.co/Carb_Kit_Yamaha_TRX850.html

[cobbadiggabuddyblooo]

Handy link to keep Dandy...
Are these kits just a seal kit or comes with needles/tubes jets ect???

[dandywarhol]

Purely a seal kit made from Viton.

The company is owned by a Scot who moved out to Thailand and set up business - their stuff is very good.

[Ubaat]

Today I have taken off the tank, carbs and sparkplugs.

And I got even more in doubt what it can be.
I did a compression test with cold engine cause I just so long time to get all the bits off.
I got 210psi on the left cylinder and about 207 on the right??? That was when the carbs was dissmounted..

The main jets was 148

Here are some pictures

[Ubaat]

Here are some more picture.

I did not have the correct size modul so I had to use the rubber fu`?er, and the rubber fell off when I was done and had to fish it up whit a steel rod. TWICE...

It did not blow black smoke when I revd it in N today.

And when I look at the plugs I wounder iff it can be the fuel pump?

[Ubaat]

By the way, does anybody know iff I can wash the KN filter in diesel??

[cobbadiggabuddyblooo]

Wash in water and leave to dry, don't use compressed air on it as it will tear the fibres apart..