Trials Australia Forums

Problem is I see all that fibre coming off and sucking on to the filter
So I added the template I made it with


A mother requirement is volume and there is plenty of space around the filter



A few cable ties to hold it all in place.


Another requirement is sucking from the top. I can easily close the bottom off but I want to see the patten that the dirt stickies to the filter first as that will tell me what it needs. It may work well like it is as its mostly up the top.

Every thing is still where I left it so reliability is there


Seems to be sucking or getting air from the front which would have to come in through the left side behind the side cover closest to the motor. I may be able to do some thing about the large pieces.
The heat shielding seems to be working. I never felt that the motor was getting hot or a change in performance. At times my leg and very right cheek were hot but that's all


The back is rues nobly clear apart from beeping dirty. So I'm thinking more is coming from the front than the rear wheel


The plug looks a smidge lean considering how hot it was. I like to run mine on the rich side.



Very happy with how it went apart from just off idle in neutral just a bit boggy there. I was court in sand in 3-4th gear a few times with no opportunity to down shift with out the expectation of getting a neutral so I slogged it out to nearly walking pase to very low revs and it never missed a beat.

Filter fome comes in 3 grades: black (useless at stopping dust, red race, and green for general purpose.


With a little templatimg


I want to stop the big stuff getting to the filter and encourage sucking from a cleaner area. The material is dry so it's just for stoping the twigs and such



I will read the filter next time I go out and see if I need to do any more. I can close the top off more but will see how this works first. Nothing is closed off on the left side.



The seat I made more or less sits on the frame sealing that off and the exhaust. There is still lots of areas air can enter filter area.

I have been thinking about the difference in emulsion tubes and main air jets between the TY and DT carbs.
My previous theories are wrong not that I know I'm right now.
The TY uses a 2.5mm main air jet and the two hole emulsion tube. This explains why the TY comp has 240 main jet and the TY175JC only a 140. The JC like the DT use a 5 hole emulsion tube with a very small main air jet. This arrangement seems to suit upper rev ranges.


This is a YZ 80 and it has a 1mm main air jet where the DT has a 0.4


Left is the TY comp emulsion tube and right top is the JC and bottom early DT with the 5 holes.
Theory is low revving motors like to have well atomised fuel at low revs. That's why they have the big air jets and and large main jets. The main jets are so large because there is a lot of air mixed in with the fuel so you have to have big jets.
The JC, DT, YZ all have small main air jets which restricts the amount of air that can be mixed in with the fuel on the way up which is why they have smaller main jets to suite.


Looking at the 2 types I mistakenly thought the 5 x 0.5mm holes would flow more than the 2 x 1mm hole but the maths says other ways !? By a long way nearly twice the amount.


I have three problems with what my motor is wanting:
1- the main jet is 360. Which is really large and only have jets for 140 through to 300
2- the needle is on clip five which is the richest. I tend to think if I'm on that edge of the range it's out of balance
3- I'm using my smallest pilot jet 2.25. Which is quite small normal is a 2.5 to 3.5. The air screw is at 3 1/2 turns out which means I need to go smaller?

I tried a #2 slide cutaway but its muddy the 1.5 is better. As the main jet is so large I tried with out a jet to see if that works but is didn't by a long way (good) standard is 2.5

I'm thinking the big air intake system and my porting on the bell mouth may be causing the need for a large main jet. So is an attempt to bring the jet sizes back into the range I have I decided to restrict the main air jet back from 2.5mm to 2mm. This in theory will lessen the air mixed in with the fuel in the emulsion tube and therefor draw more fuel and need a smaller jet. As the DT and YZ do. This carb had a small main air jet like the DT but it drilled it out to 2.5 like the TY as there is a noticeable difference in feel between the two.

The problem is how to restrict the main air jet. I used a float bowl overflow nozzle, chamfered the tip, small wrapping of electrical tape to pad it out to the right resistance and sealed it in shrink wrap. What ever I make I have to be able to reverse it re-jet to another size if need be. I have now started my own main air jetting process


I'm thinking this may be another reason for some kind of catastrophic failure if that falls out and is sucked in but should hold


I expected that I would be to rich but all it did was go better by filling the top end out. I guess i fixed my tad lean issue. I can't begin to change the needle settings till I find the celling on richness. It will do for the next ride.

I'm on the edge of a theory that puts the large hole emulsion tube at a evolutionary dead end.
The large main air jet, emulsion tube and main jet were for a small 22mm carb boar size and large low revving piston.
All the other bike variations had bigger carbs and revs. With the big holes, small carb boar, low rev, long draw you have to atomise the fuel this way as ferocity of revs is not going to do it.
By having a 26mm carb which is 28% larger than the standard 22mm but still using the small boar atomisation process I am to some degree I am drawing? (Need to think this one out more)

You may see TY175, I see YZ80 tuned for trials.


I had a dream of putting a 26 there and this is what I end up with.


My take of a old idea. On one level it's nearly not right.

Now that I think of it that chamber vas very dry. I would have expected more oil on the walls from blow back. That may mean my attempt to make the reads act like a boost bottle may be working.

The air cleaner lasted another long ride. This ride was not as dusty but still pushing through bush.
Lots of small floaties but no big bits.


Everything is where I left it and reasonably clean so I will just leave it and keep developing the carbonation.


To me it looks ok but I don't know about the black soot around the outside rim. Could be the TY fuelling system for getting a big quick gut full at low revs. I'm thinking the big main air jet, large jetted emulsion tube and large main jets are for getting good atermisation at low revs. You have to have a quick response at low revs and well aerated fuel is lighter and quicker to respond. This could explain why the main jet is so large when the carb gets bigger.

If anyone with TY spark plug reading ability can advise me on there experience with what this plug is saying I would be very happy to hear

When I first put this bike together I had to clean out an straighten one rear shock. They proved to have no compression or rebound I was bounced of the track! I was warned not to get cheep suspension but the wallet ruled so I got these Asian ones. I don't know what they were made for but they are hard. I put it at one new shock on softest spring setting on the right and one clapped out standard shock on hardest spring setting. And it works.

I am disappointed with the 26. It works but its off down low and over carbed up top. So I put the 24 back in. All my old settings that I remember and the Tioli air box.

It was off. Now I'm in a jetting black hole and am looking at re building the settings. Shorly the my mod on the standard system can't be that restrictive.

3 days later I realise I put a 16 front sprocket on the same time as the 26mm which is why I didn't think the the power was that much better and possibly less in other areas. It's not till you go back to 24mm that you notice the difference, there is less go. This could be because I put the Tioli air box on and the 26mm. The bike improved the percentage between 15t and 16t front std rear

This gave me the encourage mention to test a theory that I need to get control of just off idle to 1/2 throttle
To my calculations I need to take a mm off the slide.


Grind, file, shampfer, and fine file I modified a 1.5 which is already a small cutaway.


On the left is 2.5, seems to be a popular size and on the right is my version of 1.


I still think the bronze one looks thinner but the maths says don't worry about it and use the ty175 comp one.


Instant change, I did not realise how much improvement lay in that range. I was so enthused I modified my 26 to emulate a 24mm. (Both 26mm)
That 26 will really benefit from a small cutaway. The 24 was better than the 26 again. I'm sure I'm going to need the 26 size some time.


I was in a shape it first and fix it later kind of mode. Knocked the brass bung in the pilot air passage, deep in its hole to it started to interfere with the pilot air jet.
I assessed the break through as minor. The air flows to the right and there is a seal up the passage. Minor turbulence

Tioli. 7 RRRRRRR. "A moment in time".


My bikes have spirit.