tobster

feetupfun is spot on. IF you are doing loads of large throttle opening stuff then add more oil, BUT if you're doing trials stuff i.e. small throttle openings, then I reaffirm my recommendation that 70:1 is more than enough oil. I seem to remember the Yamaha manual recommnends 50:1, presumably to cover mixed riding i.e trashing down the road & pootling in a field/ditch as well as adding a huge manufacturer safety margin, but that was over 15 years ago!!!! As with many things, oil technology has come on a long way since the 80's. Therefore with the quality & protection offered by modern synthetic oils (any brand) there is absolutely no need to add this 'extra' oil - it's just going to gunge up your engine/exhaust/polute etc. I would also suggest that using the spark plug to gauge the correct amount of oil is a dangerous game. Spark plug colour is surely used to determine/record/observe the fuel:air mixture levels and not oil (though of course there is indeed oil in the fuel). Of course be aware that if you change your oil:fuel ratio then you will also be changing your fuel:air ratio. Phew.

you could always get a manual from Birkett motorsport (01229-716806) - they will also be able to give you the definitive answer to most of your questions eg oil/fuel ratios, tyre pressures etc. They are also a good source of spares, should you need them.

re your oil questions, I use Silkolene comp 2 pre mix oil at 70:1. For the gearbox I'm using Dextron II ATF. As you have dirt bike experience, you might think that 70:1 is way too lean on the oil, but for trials work, and with a modern syntheitc oil, this is more than enough oil. You shouldn't be reving the nuts off it (unlike a MX bike), so this amount of oil is sufficient. Remember if/when you're running the tyre pressures recommender by feetupfun that you must have those things to stop the tyre spinning on the rim (I can't remember their real name..old age creeping up on me again).. ah yes, security bolts, phew I though I had really lost it there. that's enough for now.

also for better/more responses try posting in the gas gas section though I guess if you do that now then admin might flick your ear for repeat posting?

re the lack of low down power, I fear you (or rather the child) may be stuck. Our TXT80 is gutless at low revs & eventually gets going, almost like turbo lag. My boy is not finding it the easiest bike to ride having changed last year froma ty80, though some of that is because it is a much bigger bike. Our bike also runs mega rich when used as a trials bike (i.e. it's fine when you do 1/4,1/2 and full throttle plug chops) so I have been tinkering with the carb to get it to run better i.e leaner. I personally would try the carb settings for the 50 and see how it runs before you start buying bigger jets/slides and needles. A short ride to these carb settings will not damage the engine - do a plug chop and see what the plug looks like. Also run the fuel:oil ratio at 70:1. Good luck

Alan did you manage to find any details of the rookie carb mods you mentioned - what were they supposed to do/improve?? the only mods I've found (on the gas gas USA site, Jim Snell) are raising the needle to full rich and cutting a v in the slide (though the picture/details are too small to see them accurately enough to actually do them).

getting a little excited as I (with your help) may have sorted the problem. One ride and all is still well. Guess what it was?...give up - well here's a clue - it costs about

I'm getting the feeling that mixture may not be the only problem as the plug is quite wet - to me this points towards a failing wet side crankshaft oil seal. Whether this would screw up the carburation I don't know, especially relating the lack of adjustability of the fuel screw. Good idea - I'll have a look at the condition of the fuel screw tip tonight.

hi Tony Thanks for the reassuring answer - hopefully someone who has actually worked on one of these bikes/engines will be able to confirm your answer...presumably you 'just' dig out the old with a screwdriver and then push a new one in. Is there anything to be gained by cooling the seal to help it slip in easier or does that trick only work with bearings?

Hi Is it possible to change the transmission side crankshaft oil seals on a 2002 rookie without splitting the crank cases?

so James, good to hear your brakes are brakes again - out of interest, which bleeding method did you use after all & did you try the mystical bungee on the lever overnight trick??

James Sometimes something can be better without actually knowing the reason why. Eh??? Not having a rational explanation does not make the observation or statement false, merely unexplained....Confucious

thanks Steve for the input - an interesting topic. Unfortunately I don't think I can fairly blame the Silkolene oil (yet) as not only has this bike only had about 2 tanks of Silkolene, but when I bought the bike it was already running badly (very reluctant to start resulting in good price haggle), and he was using a general 2 stroke oil at 50:1.

hi it's actually a PHBG 21DS which may be similar to the PHBL (I'm not sure). According to the Dellorto agents (Eurocarb), it has a fuel screw and NOT an air screw. Apparently the rule is that if the offending screw is nearer the engine than the air box, then it is a fuel screw, and an air screw vica versa. Sooo, turning it in (clockwise) will restrict the fuel flow, making it leaner. Of course this all contradicts that gas gas USA spec sheet, but I would tend to believe a carb specialist over a general bike specialist. That article also recommends richening up the needle, when it is certainly not lean at the moment. Hence loads of conflicting advice...... Incidentally I have set the screw at 1 1/2 turns out though it had no effect on the way out from completely in to completely out. Surely an indication of richness?? Help

indeed there may be nothing special about silkolene, it's just i've been advised by gas gas UK to steer clear of it with gas gas. It seems to work well enough in my Pinky though I'm more than happy to try another brand providing I can hold of it easily. We've only just got the bike and it came starting badly. I've put in a new NGK BPR5ES & since checked and changed the pilot jet (50). i've done plug chops at the various throttle openings and all seems well, though it is probably on the rich side, especially at small throttle openings. I've increased the float level to just over 16mm, trying to lean off the whole carburation. Fuel is switched off at end of ride. Float needle seems to work, though I only gauged this by blowing throught the fuel line. As I understand it, the mixture screw on the TXT80 is a fuel screw (as it's in the front of the carb), so I don't undestand why screwing it fully in i.e. reducing the amount of fuel, doesn't cause the engine to stop. Clearly the engine is getting fuel from somewhere else. The needle is in the fully lean position i.e clip in top position. What's going on?

After years of pumping from the reservoir down to the caliper, I, like Charliechitlins, now use the puminging from the caliper approach. It's much quicker, & very rewarding when great (& even small ones) bubbles surface in the reservoir. Also the trick by Ask Greeves, is supposed to work very well - used by a friend of mine many moons ago when we both did production racing - I person got a good firm braking system using just conventional bleeding techniques.

why doesn't anyone use silkolene in their gas gas? Also, how much of a difference to the fuel mixture (in terms of rich/lean) does using different fuel:oil ratios make? I'm currently using 70:1 (silkolene pro) with a TXT80 and the bike runs rich & the mixture screw has no effect upon adjustment - presumably using more oil will lean it out slightly or should/can I just increase the float height to say 16.5mm? The bike starts fine from cold with no choke even in this weather, but stall it hot, and it's a beast to start - bump starting works, then it runs fine - what is going on?

Hi Pandelboy My W7 needle clip is also in its top slot - so your pilot was a 60 or did you also misidentify the jet like me. Do you know the spec of the starter jet? Also what happened to that email you were going to send me or did I misunderstand your email? I shall keep all informed of my progress. Off to get some Dextron III ATF this lunchtime for said beast - hopefully that will aleviate the clutch drag. If it does, perhaps I'll put some in my TY250R. Later

and don't overoil it as not only is it wasteful, in my experience, it can make the bike run rich (though I have to add that was a ty250). In fact to avoid this potential problem I use an aerosol foam oil filter (PJ1) rather than the liquid method. Of course you must always clean the filter properly (again PJ1 of course) & let it dry properly

hi guys thanks for the input. Actually on recieving a 50 pilot jet from gas gas (next day delivery and very good service etc), it seems I was mistaken in identifying the 'problem' jet as the pilot jet. It looks like the jet I had identified as 60 is in fact the starter jet (a long thin brass item whose spec I can not find) - is that same as your Pandelboy? The number on my old pilot jet ( a tiny item located between the main jet and the starter jet) is impossible to read, but I think I'll fit the new one anyway. Searching around it seems that if the air screw adjustment causes no effect then it means that the pilot jet is the wrong size - perhaps I'll find that my pilot is a 60 after all which would be spooky!! Re the plug deal, having spoken to a number of gas gas dealers, the concensus is to use a BPR5ES and not a B9EG, so that's what I'll do. I can see a liitle weekend of tinkering ahead (& I haven't even got around to replacing the leaking fork seal or sorting out the dragging clutch...). Made me realise what a cracking bike the TY80 was/is. Later

Hi A slightly long ramble so please bear with me - baaaaa (that's for the oldies amongst us) I've just acquired a 2002 TXT80 rookie for my boy to replace the TY80. Whilst doing a bit of initial maintenance as the bike is a beast to start, I noticed the spark plug was very black. Upon closer examination the type of plug appears to contradict what all the 'books' say I should be using. The plug in the bike is an NGK B9EG, whereas it seems I should be using a BPR5ES. These 2 plugs seem miles apart in both temp as well as appearance, so what's going on?? ALSO, whilst trying to check that the jetting is OK by plug chops, I noticed that adjusting the air screw had no effect - the colour of the plug was however good throughout the throttle range. When I opened up the carb all was as expected , except the idle jet was a 60, when I had been expecting a 50. Also the needle was in its lowest settings (i.e. the clip was at the top of the needle). What does this all mean (apart from someone has been inside this bike tinkering) or are these pukka modifications? Any comments wellcome re what people are using for this bike PS What's this I hear about Silkolene (in the fuel) not being recommended in Gas Gas? Are you still here - good, well that's it - I'll sit back and await the barrage of useful info......