Cynic

I think you are about right with the air filter letting her go lean, its not a perfect fix but as an exercise leave the float height and pilot jet at std settings and lift the needle a click and see if that has an effect, if it does then try upping it another step and check again if a couple of points up gets it somewhere near then you may be able to leave it at that. Or chuck a bigger main jet in. If you are in the desert then the oiled sponge is prob a better filter for you situation and the hot air will mean (i think) that you won't be as lean as i would be in our stinky UK wheather mix of hot,wet,cold,dry mixed any way you fancy every 20 minutes.

Amen to that, assumtion and missus in the same sentance has GOT to be trouble.

My best man had something similar, found his regular route, bought himself an old shed of a van, then made sure he was in front at a set of lights and nailed the brakes when they were on green, then drove off. Dumped the van just as soon as, job done. One very expensive repair job on his pride and joy.

C'mon jim were talking DREAM garage here, yellow and black cos i like it, as i recall the DX had the CDI ig rather than points, wheels for some decent tyres and brakes and the monoshock cos i can. I have worshipped them from afar for years and ONE day i will have one. Nearly bought a few over the years but mostly they are like the last one a while back the 'needs tidying few bits to finish' could have been written by a Sun journalist. I think the Suzuki may go to make way for one in the future.

There is nothing more optomistic than a ped speedo, seriously WF do the math and you will know how fast you can go, if you jury rigged a rev counter you would be able to get the bikes speed almost exactly. An rd 50 of the same vintage could donate all the parts for a mechanical one, they are just not fitted on the DT. All the machining has been done.

Right you recon your mech theory is pretty good try this..... Assume engine at max permitted rpm say 7500 Primary ratio (crank to clutch on my 175) 3.227-1 so 7500/3.227 =2324rpm Now assume top gear 0.8-1 so 2324/.8=2905rpm Final drive 3.267 so 2905/3.267=889rpm So the rear wheel at 7500 rpm is doing 889 rpm Rear wheel at roughly 18inch dia (45cm) circ =PiD 3.14*45=141cm /100 to 1.41m per rpm so multiply by 889, therefore 889*1.41=1253m per min so multiply by 60 hence 1253*60 =75209m so theoretically when my dt is at 7500 rpm it is doing roughly (due to the estimate on the rear wheel)75kph (ironically) you can use that lot with your own manual to calculate the exact speeds of your bike, and the maximun theoretical speed. Should save any guesswork with the sprockets.

Crikey man if you have a 12 on the front no wonder you are getting 40mph, get the 14 in soonest then find a long hill and see what you get up and down, and you could get a 15 once upon a long time ago so i don't see why not now if need be,

Sorry mate, i honestly thought it was from a RS. It was quite small and i ran it with a 14 i'm sure as the 15 was too tall and got a LOT more than 40mph. I did have the dt50m not the MX (similar to a TY)so maybe that is a difference. Either way if you dig around i'm sure you will get one that fits that is the right number of teeth. Don't just limit yourself to yams either. No reason to exclude other manufacturers. There is a lot more to gearing than just the sprockets, but ultimately you want as small as you can realisticly get on the rear for road performance and use different front sprockets to match it up right.

Easy an RD400DX in yellow and black speedblock with spannies and a full stanstephens tune, top deck ohlins cartridge forks and monoshock conversion with carbon wheels and a deep braced satin black ally swinger. I could go on but MMMMMM i need a moment. You can keep all that other rubbish.

Companies are lazy, now modern motorcycles need fancy this that and doodah to sell. Back 'when jesus was a boy' as there are only a couple of chain sizes they generally kept the pcd on a wheel hub the same so they could use it for say, the 50, 80, 100 maybe even 125/75. Just look at suzuki, within reason all the oil cooled bandit stuff swaps with GSXR stuff wheels everything. Then all they had to do was lace it to a different rim, manufacturing cost zero. If i remember right ( i may be wrong it came from a breakers ) it was a rs100 rear sprocket on the back of my dt50, i know i couldnt pull the biggy on the front with it and i could get 65ish (clocked at 64) in PERFECT conditions reving its b@lls off , realisticly it was more like 45-50, with i think a 14 but in really windy stuff i was better running a 13 maybe even a 12 cos the engine was so peaky. You really need a friendly breaker who will check or better still you do it. Again back in the day breakers you could actually go to were pretty common now its all online. And health and safety cobblers means NO BODY will officially say it will work in case you sue.

+1 Either the points have closed up or they are bridged in some way. You are performing the same function switching the ig on and off, as in stopping the primary voltage to the coils which is what generates the spark. The one good point from this is that everything else must be ok for it to spark. Have a close look at the points they may have slipped.

Wouldnt be running with lights on? Battery getting a hammering so is calling for juice from the electrics but they are also running the lights. All this slows the idle speed and if it was a little slow to start with. Put a 1/8 of a turn on the throttle stop to speed the idle up. Should sort it.

Right i know this is prob going to sound a bit nuts and its nothing to do with dewpy, this is serious, true. I was driving along the A47 today past Desford (Licestershire) when i saw what looked like and i was sober, a SR125 that had been EXTENSIVELY modded to take some sort of old V4 pre unit lump, and i mean old like exposed pushrods and such. It was an inline vertical 45degree V layout, also for some reason a hard tail????? with a sprung seat and was toodling along in his own sweet time at about 40mph. It had MRA on the black tank and had C120MRA as the reg, anybody got any ideas, he was heading into Licester with what looked like his work bag on his shoulder.

Oh so many thoughts, so so many........

No worries, without people prepared to stand stand up and be counted this forum would not be what it is. There are plenty of forums that only ever seem to talk about which oil or what tyres and won't even cosider telling someone something that may (shock) upset them,ZZZZZZZ. Good to know you completely ruled out the carb, with good mechanics that only leaves ig. Take it away jim....

Fair point, Yamaha also assumed his bike would be scrap after about 6 years and it plainly isn't, time can be the cruelest master and what he has described is pretty much what my dt was doing a while back after it had stood through the summer, some petrol residue had screwed up the carb internal passageways in the choke and it took a lot more than most people class as a clean to clear all the tiny galleys. All it was was a little bit of shit bobbing around screwing the mix. Lean one minute rich the next. Fires on choke lovely then the mix goes lean, it farts about and dies. If you want to be the only contributor to the jim forum fine, start one. It says Yamaha owners at the top of the page and thats what i am. We are'nt always right, but we try to help. And that is what its all about.

Never being one to assume, what you are discribing could be caused from a bad fuel level or a slow feed, it fires initially cos there is just enough in the carb and then runs out. Your description of a big fat spark and the fact that it fires first kick every time makes me think carb. I know you have done it but they are very sensitive and float height is especially critical on 'performance' strokers. I could be wrong but most engine running probs are generally carb related. Most of the time when the ig goes up sh1t creek it just wont go at all.

Why did you not check using the battery and some wire like i suggested instead of ripping into the loom? The yellow is powering the ig coil and the brake lights and we know all that works, the BLUE one is the one you want and that starts at the headlight, as in a connection behind it, and runs to the tail light do not pass go do not collect your 2oo quid. You can check the continuity as you can get at both ends to prove it, you have proved the tail light. If you find this to be ok we can move on. A dodgy taillight is nothing, when i was greenlaning my 175 regular i was going through em all the time, smashing them or filling them and the bike (and me i suppose)with sh1t. And i mean sh1t, cow and horse probably and nothing f'ks your bikes more delicate components quicker.

The yellow from the main beam switch and the blue at the back of the bike are completely un connected, the headlight runs solely on ac if you run a jumper to the headlight you will be putting AC into the battery , use the battery and take a jumper from that to the blue tail light connection. If that is good get behind the headlight and do the same to the blue wire from the lighting switch. The line to the taillight comes straight from there,

Does he have a choice...........

What does the 'oil' feel like, brake fluid has a thin watery feel to it, wheras the fork oil will feel like, well oil. If its not coming from the brakes then it must be coming from the forks. If it happens within 100 yards it must be visible, give the front of the bike a good degrease. Make sure its bone dry then go into the house and pinch the talc from the bathroom and cover the front of the bike with it. Now ride down the road with your bike smelling loverrrly. Apply the brakes, get off and look for the damp spot (missus). Its not very scientific but can't see why it shouldnt work.

Bad news then, you need to find and fit either the correct coil or the correct cdi.

I haven't the faintest idea what you are on about with the X factor but the BBC does seem to be generating tripe at the moment. Excepting Heroes, I admit i like that.

Er Goff, its on itv......

Some have a 7 wire and some have six, the important point is that the cdi needs to match the stator ( behind the flywheel) as the 7 wire uses 2 source coils for the cdi wheras the 6wire system uses 1. What it sounds like is you have the low speed coil connected to your cdi which won't generate the right voltage at higher rpm to trigger the cdi accurately giving your bad spark, does it go ok at realy high rpm? As in 7-8000....