spark

Hi Chaps, just an update on what I found. The culprit was split needle roller bearing MT280236161 on the secondary shaft. I flipped the one half over so you can compare the good cage side to the bad side. There is no real reason this should have happened that I could find. I micrometered the shaft and bore and both are spot on. It was the ends of the splines that ate the side of the cage away. All I could really do to help prevent this in future is chamfer the ends of the splines and give the ends a polish with 1000 grit water paper. I also found that the primary shaft was tight. I could turn it by hand if I grabbed really tight. With the paper center case gasket squishing when bolts are tightened it made the cases too close together, or perhaps the distance from the circlip groove to the shoulder on the shaft was a bit over spec. I ended up grinding 0.05mm off the circlip on the surface grinder and that gave it 0.02 clearance. Also gear 5 that ran on the damaged needle roller was really tight with it's circlip on and you could see how it had worn the washer. I used an oil stone to take off 0.04mm from the circlip and it runs sweet now. I do not know how they even assembled it like that, the circlip should not have even gone on without some serious force. All in all after working on this motor I am impressed with the engineering behind it, but I can see they have made some compromises to make it this light and compact. It is also evident that they do not take care to ensure everything is perfect when assembling either. However I love these gassers so I am willing to put up with it. Thanks to all who gave advice!

Hi chaps, I bought a 2011 TXT Pro 300 recently with extremely low hours on it. Including the riding I have done it amounts to about 20 hrs. You can still see the square shaped grooves on the tread blocks on the original back tyre. As part of maintenance I drained the gearbox oil to find the usual small bits of metal on the magnetic drain plug, but also this piece as well. I cleaned the drain plug and stuck the shaving back to give a reference for size. These are pics under a low power microscope- Now that I think back I did battle once on Saturday to get the bike into second gear from first. This was with a light lift of the foot, with a hard pull it went in. Then on Sunday I remember thinking to myself that the box felt a bit more notchy than usual. It was not bad but it did catch my attention. The steel is hard and when I tried to flex it between two pliers it broke instead of flexing. My first guess would have been a needle roller cage but then I thought that the cage would be out of a softer metal.... So do you guys have any idea where this piece may have come from? Do you think I should split the engine?

I use contact adhesive. Clean both surfaces with acetone or thinners. Apply thin layer to airbox and thin layer to mudflap.Press together when touch dry. Make sure you line them up properly as you cannot adjust once they touch. Works very well.

That is a front wheel he has broken. Lian surely you can bring in a set of spokes, nipples and rim, or even a complete wheel from places like Lewisport?

Lian, also check to make sure the swingarm bolt (the 20mm long mushroom head bolt that screws into the swingarm pivot shaft) has not snapped its head off. It is hollow so it can break fairly easily.

Aye I heard you the first time! I would like one of these for use in my back garden, but it would have to have a clutch and be able to splatter. Looking at the vid I didn't see any of that going on just pivot turns.

First of all as Gronno mentioned there seems to be water in that oil. Are you sure it is not leaking from the gasket that joins the two case halves?

Hmmm you know Neo there are some seals on the bike where I would only be happy to use the originals, water pump seals being one of them. Without looking at the quality of the aftermarket seals it is hard to say, but as mentioned I would prefer a dust seal. Have they changed the shafts from 2001 to 2006, coz I have this spare one I made sitting here doing nothing I could send to you.

Hi hubba, as Jon mentions check the clutch hub capscrew. It should have a hole drilled through it. A mate of mine had the same problem you describe and after stripping the engine down completely twice he finally discovered he had replaced the vent screw with a normal cap screw. Replacing it with the correct screw fixed the problem.

When I had my 2001 Sherco I turned up 2 new shafts (1 as a spare) out of 2316 and had them nitrided. 2316 material has the advantage that it does not corrode because of the high chrome content, and when nitrided it has a very hard skin. I would not use brass, it is too soft and the seal will cut a groove in it even faster I would imagine.

Alrighty my Gas Gas Racing model arrived last week with the PWK 28 carb. The bike runs amazing with this carb on! The bike runs so crisp, not a hint of richness. I cannot feel a loss in bottom end, and the bike picks up revs much quicker with more power as well. The odd pinging I used to get with the Dellorto is not there and I am getting better economy as well.To say I'm pleased would be an understatement.

Jon you are a very reasonable fellow!

When I say darker colour I am talking relative to the original colour of the oil, not dark in colour. I use ATF and it is a translucent red. When it starts to become not as translucent from the clutch particles I do an oil change. This works out to around 6 oil changes a year for me. As I am not fortunate to be able to ride on a fixed timetable it works out that I ride a lot more some months than others. I basically would have 3 options to keep track of when to change the oil. 1. Use an hour meter 2. Write down in a book the hours ridden 3. Use the colour of my oil as a guide I choose 3 because it is the easiest and if you look at the recommendations suggested 6 oil changes a year seems to be ok. I like doing splatters and jap zaps so my oil does not take long to get contaminated with clutch particles. I suppose if this is not your riding style it would not be a good way to gauge when to do an oil change. Have you ever looked at the condition of the oil that gets drained out of your motor vehicle sump, and that does a harder job of lubricating the pistons, big end, cams etc. I will however do a flush and oil change immediately if the oil gets any water in it whatsoever.

I just take a peek through the sight glass. When I see it changing from a red colour to a darker colour from the clutch plate contaminants then I do an oil change.

Ja grip glue is contact adhesive at a couple times the price.

I have broken several airboxes.... Contact adhesive works very, very well. Apply as per the instructions on the tin or tube.

I like the sight glass. I can see when it is time to change the oil either from clutch plate contamination or water sucked in through the breather.

I have completely bled my rear brakes 3 times already for various reasons. I know I should struggle bleeding it from what I have read, but actually every time has gone very easy. I use a combination of sucking and pushing the fluid with the syringe. It is a couple minute job.

I actually got my syringe from the local shop as it was sold as a basting syringe (comes in a packet with a needle and instructions). Alternatively a horse vet cos damn I don't want to think they could use a syringe that size on a human...

I have quite a bit of unwilling experience in this department. The first thing is to imagine how air will act in your brake system. It only takes a very small bubble to have spongy brakes. If there is a loop in your brake hose before it drops down to the master cylinder an air bubble will want to sit there. A little corner in the caliper higher than the banjo bolt and it may decide to hide there as well pulling faces at your fruitless bleeding attempts. I find the best method is to use a very large syringe, like 60cc. This is connected to the nipple on the caliper with some rubber hose and the fluid is sucked down from the master cylinder. I actually made a larger reservoir from a Motorex brake fluid can that bolted to the top of the master cylinder so I could add lots of brake fluid. If you do not do this you will need to have someone to top up the master cylinder as it drains extremely fast. Sometimes if the brakes are being very stubborn I may reverse bleed as well by filling the syringe with brake fluid and forcing it up into the master cylinder reservoir. Loosening the caliper from the fork and dropping it lower helps get rid of the loop in the brake hose where bubbles like to sit. Lightly tapping the brake hose and caliper also helps dislodge any little bubbles as well. Rotating the caliper so the banjo bolt is the highest point helps as well. I like to end off by turning my bars so the master cylinder is the highest point in the system (caliper still hanging down to get rid of the loop). Then I flick the brake lever in and out whilst tapping the brake hose. Normally any left over small bubbles will come out of the hole in the master cylinder. It may be a good idea to change the seals in the master cylinder whilst you are at it. My bike was less than a year old when my brakes were not as good as when the bike was new. New master cylinder seals brought back the instant hard brakes and got rid of the mushiness. The pistons in my caliper are also coated with what looks like a titanium nitride. I polished the matt surface with diamond paste and a felt bob in a die grinder. Doing this made the pistons slide much easier and got rid of the tick tick noise I would hear from the brake pads touching the floating disc. I can tell you a last resort, but this really is a last resort that I had to use once. I am extremely fussy with my brakes and the one time I just could not get that rock solid feel to the lever no matter how much bleeding I did.It worked fine but it was not perfect. I bought 5 bottles of 500ml brake fluid and filled up an empty 2L ice cream tub. With some latex gloves on I assembled the brake caliper completely submerged in the brake fluid, making sure there was not even the tiniest air bubble, not even behind the seals. Filling up the syringe and reverse bleeding the brake hose whilst having the syringe and caliper submerged guarantees that you cannot introduce any air into the system. This was done on a workbench, not still attached to the bike. Using this method I got brakes that were as good as new if not better. Quite unconventional but it worked damn well.

Howzit! I am also waiting for a 300 Racing model. As you can see I have the 2010 standard model. Two of my friends have the 2011 standard models as well and I have ridden them a bit. The only real difference between my 2010 and 2011 standard models that I can feel is the new bike feels a bit wider, what with the bigger airbox etc. Other than that they feel the same to me. I am however looking real forward to the Racing model with the PWK 28 carburettor and Ohlins shock. Actually the wait is eating at me, and being in South Africa it will be a month before they arrive.

Yes 100% correct Baldilocks. I thought he was referring to a master cylinder with a larger piston diameter. I know I was researching them when I wanted to make my clutch action faster. I landed up moving my perch closer to the bar ends which did the job of making it faster. Moving it further away from the bar end will make it slower and more progressive as everyone suggests.

If a discussion on sparkplugs can reach 3 pages with all the engineers crawling out the woodwork, imagine the potential this thread has! I have always broken in my engines in a similar way to what is suggested in the article, and my bikes have always been good performers be they road, enduro, or trial. Of course I can't say they would have been any worse had I nursed them till worn in, which seems to be the common method. I don't see why the method would work on 4 strokes and not 2 strokes. Bedding in rings is bedding in rings, the principal should remain the same. I also like to "feel" my engines when running them in if that makes any sense.

All things being equal a larger clutch master should make the pull harder and the clutch action faster. Which clutch master are you thinking of using?

Instead of having to deal with the pros and cons of 26mm vs 28mm I wonder why the manufacturers don't make an oval bore. Say 26mm extended to a height of 30mm. I have read of oval bore carbs before, surely it would work well on a trials bike.