dt502001 Posted September 20, 2012 Share Posted September 20, 2012 Yes the # stapmed is the jet size.The pilot jet is for closed throttle to @1/4 and verry small factor in the rest of the range. The air and pilot as well as different needle sizes and shapes are for fine tuning.For a different type of power delivery like a track wher your mostly in the midd throttle openings or rmp with realy short burst to high rpm you would jet it leaner or vise vers long track with realy high rpms most of the time =richer Jetting your bike in coolder temps will mean it will be rich when it warms up again Cold air is thiner with more o2.Ie: when I ice race i go up 1 size on the main and raise the needle 1 noch( normaly the cilp is on the 3 from bottom so it goes to 2nd from the bottom) then everything goes back for the summer. I would still suggets you put the stock pipe on to break in the new top end. But if your set on using the new pipe. Make sure you get all the melted alum out of it as well. Then jet big 2 or 3 sizes( normaly 1 is good for a pipe change) bigger and raise the needle 2 notches this will make your bike rich in all the ranges of throttle opening.And make it safe to do a plug chop Now you start working backwards slowly, after riding it and checking your plug colour but don't let the bike idle this will give you false readings. Start moving the cilp back to stock 1 clip at a time and checking the plug if you get back to stock and it's still rich .Then put in the next smaller down in main jet size and raise the needle again and start doing all the above over untill you get a nice brown plug at high rpms.When installing the float bowl bolts don't crank them down as hard as you can just tight or you will have a hell of a time getting them out again.Personaly I throw out the stock philips bolts and put in allen Also you should check your oil pump for proper adjustment and out put that massive melt down could have been the result of the pump not working properly. Also flush the oil tank and lines to make sure nothing is possibly blocking the oil from getting to the pump.The safe bet is to pre mix and forget about the pump Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 20, 2012 Moderator Share Posted September 20, 2012 .The safe bet is to pre mix and forget about the pump I know this is a some do some don't issue but junking the pump is the worst possible idea. It is a wonderfull piece of kit that saves hassle all ways up. I have been riding 2 strokes for 25 years and pumps break because people think they are not working when they are after blaming siezures on the oil pump rather than looking for other possibles. Airhead and i were talking about the pumps at squires and the fact that when the bike is not being worked hard the oil drops right off. its true, last year i used 2 bottles over the squires weekend over 500 odd miles. This year i used nowhere near that, i traveled up slower on b roads and rode with the 175s on the rideout so basically bimbling along. The thing is i didn't use massively less fuel. Less on the rideout but 2 tanks each way traveling to get there. Like flydays siezure as another example, everybody jumped on the mixture, some went for oil. none of us expected the wrong piston, every day is a school day. I would go out of my way to fix the pumps on either of my bikes. Leave the pump, it hasn't changed in 30years so it can't be all bad. Link to comment Share on other sites More sharing options...
Consmos Posted September 20, 2012 Author Share Posted September 20, 2012 Right guys here's where we're at so far: I've managed to rip the carb out after having a hell of a time trying and failing in getting the airbox off - it simply didnt leave room to manouvre the carb out, had to use more force than i was happy with. There's simply no way it's going backnjn unless I get the airbox assembly out of the frame - does anyone know how?? I removed five bolts attaching it to the frame and two bolts holding the rear mudguard on, which also join the airbox to the battery housing,but i cannot for the life of me get the damn thing out! It went in at some stage so I know it comes out, and the haynes manual says it comes away from the frame but doesn't elaborate. I also cannot seem to get the float bowl screws out without chewing them off and wrecking them, they're pretty soft and they're in there tight!! But on he upside this is the most technical i've ever been so far with a bike, thanks to the forum and the Haynes! Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 20, 2012 Moderator Share Posted September 20, 2012 yeah the carb is difficult to get in and out I remember that, however it is always done with the airbox insitu, I dont even think you can get the airbox out without removing the rear damper! It's not necessary anyway so leave it in. You may find that if you fit the carb inlet into the airbox duct first...then force it all rearwards the duct will 'give' and you can swing the front of the carb into place into the reed assy....Thats how its done IIRC If all else fails with the bowl screws you may have to get a grip of them in the sides of some mole grip jaws to undo them. I would replace them with stainless cap screws, buy those along with your new jet(s) Link to comment Share on other sites More sharing options...
Consmos Posted September 21, 2012 Author Share Posted September 21, 2012 Got the jet out! Turns out its a 4/042 hexagonal size 210. So if 210 incinerated he piston, is 250 a big enough gap or you reckon I should go higher? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 21, 2012 Moderator Share Posted September 21, 2012 the key is...to find the one thats too big and causes the engine to cough and splutter when the throttle is fully opened, then start downsizing until it runs sweet. It's a bit guesswork at first but jets are cheap even genuine mikuni ones, id be surprised if you needed any bigger than 250 but buy a few sizes...they go in increments of 10 Link to comment Share on other sites More sharing options...
dt502001 Posted September 21, 2012 Share Posted September 21, 2012 Hmm that funny I have 215 220 225 jets increments of 5 .Going from a 210 to a 250 would be 8 jets sizes from stock ,,never in my life have I ever seen that big of a increase not even on a fully ported.060 motor. on race fuel. And I have been riding/racing and servicing 2t for 35 yrs. Bigger jets are only adding more fuel not oil with the pump as it will still only be pumping the same amount of oil . You don't need to pull the carb off to change jets just turn it in the rubbers to access the screws. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 21, 2012 Moderator Share Posted September 21, 2012 Hmm that funny I have 215 220 225 jets increments of 5 .Going from a 210 to a 250 would be 8 jets sizes from stock ,,never in my life have I ever seen that big of a increase not even on a fully ported.060 motor. on race fuel. And I have been riding/racing and servicing 2t for 35 yrs. Bigger jets are only adding more fuel not oil with the pump as it will still only be pumping the same amount of oil . You don't need to pull the carb off to change jets just turn it in the rubbers to access the screws. Dont forget were stuck with 12hp in learner trim. With the pv tweaked and a pipe these motors could be getting on for 20+hp if they are done properly. Link to comment Share on other sites More sharing options...
dt502001 Posted September 21, 2012 Share Posted September 21, 2012 A yes I do forget about you stupid law.12 hp is a joke my riding lawn mowor make 18hp. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted September 21, 2012 Moderator Share Posted September 21, 2012 The predecessor to this model had a 240 jet as standard, mine ran sweet with a 250 on there but I'll admit it may be a jump too far...Judging by the degree of damage though it's likely to need a fair bit bigger than 210 The Hexagonal jets are in increments of 5 from size 50 to 195 and in increments of 10 from 200 to 500 Link to comment Share on other sites More sharing options...
Moderator Cynic Posted September 21, 2012 Moderator Share Posted September 21, 2012 It may run leaner due to emmission rules, even though its a 2 stroke they were trying to make em cleaner. Compared to the old 175's they probbably run far tighter limits on fuel and oil so suffer quicker if its a bit off maybe? Link to comment Share on other sites More sharing options...
Consmos Posted September 21, 2012 Author Share Posted September 21, 2012 I'll buy a handful, they cost almost nothing compared to another rebuild so i don't mind wasting a handful of coins if it means treating the engine well! My intention is to have it fully derestricted although noone seems 100% about how many restrictions there are, I read a lot of apeculation. No intention of carving up the manifold as the benefit seems negligable, I'd just buy a new carb if it came to that. My power valve appears to be fully open and functioning, i can't see where it's supposed to be pinned? And it's definitely orientated correctly. The CDI has been grounded and the new exhaust system was going to be the final effort to get some pep out of it... Hell maybe it did work, I didn't have time to find out! Link to comment Share on other sites More sharing options...
Consmos Posted October 12, 2012 Author Share Posted October 12, 2012 Well quick update so far - I'm having a hard time getting hold of a couple of things, mainly paint and a new seat cover. I checked with Yamaha and the closest match to original I can find is from bikecolours.com in England. They have stock of what they believed was the official match to the deep purplish blue but arent selling at the minute due to a disputw with a customer who argued that it wasn't a good match. Bikecolours are sending me a sample free of charge to test out and report back to them! Ordered a seat cover from portugal and sadly the quality is that of a poor rip-off Anyone know where to get one? One industries and factory effex do some pure awesome covers but not for dt125's, seems that nobody sells them for this bike, not even Yamaha! Haven't managed to flush out the crankcase yet as the bottom engine bolt is totally seized. On the upside, new jets have arrived and when I get a chance I'll stick up photos of what a bit of halfords radiator paint, clear laquer and elbow grease can do for severely rusted radiator mountings Link to comment Share on other sites More sharing options...
dt502001 Posted October 12, 2012 Share Posted October 12, 2012 Just a quick note you can't flush out the crank through the drain plug you have to tip it upside down .Still not a fan of that method but it's your call. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted October 12, 2012 Moderator Share Posted October 12, 2012 Personally i think the only way to de restrict them is junk the cyl completely and use the left side of a tzr250 motor. I understand (DONT BLAME ME IF YOU DONT CHECK AND IT DONT)it fits the crank induction bikes. The transfers and main ports are huge. Use some of the wiring and the cdi and there should be good power. Its what i would be looking into. When they built the old bikes they put restrictors in to save money so they could use the same bike across europe. With modern distribution and msrket demands that is redundant now. I think its easier to just make it make 12hp. Cad design would allow you to change the ports to give 12hp easy enough. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 12, 2012 Moderator Share Posted October 12, 2012 when I wanted a colour match (aerosol) I went to my local motorfactors shop and trawled through their many colour chart books for old cars, comparing them against the colour of my original painted petrol tank. When I found something to match they mixed it for me and wrote the code on the can for future ref Link to comment Share on other sites More sharing options...
CorradosandYahas Posted October 12, 2012 Share Posted October 12, 2012 Colorrite.com had deep purplish blue last time I checked. Or take airheads advice and have a local coatings shop mix you up a can. Link to comment Share on other sites More sharing options...
Consmos Posted October 15, 2012 Author Share Posted October 15, 2012 I tried halfords, they're not the most educated bunch so far and could only promise a 'close enough' job, I'd prefer exact match if I can find one... Colorrite don't seem to ship to the UK, and B&Q don't mix up aresols, just buckets. Found a couple of local folk who mix paint but again, not in spray cans. I spent ages searching for the correct colour code for the deep purplish blue then tried to buy some from Yamaha... Not only did they not sell it but they were able to tell me instantly that the colour code I had was wrong and that I shoulf have just asked them in the first place haha Link to comment Share on other sites More sharing options...
Consmos Posted November 17, 2012 Author Share Posted November 17, 2012 So here's the score: I've flushed out the crankcase (and you should have seen the crap that came out, never mind the pile of aluminium that came out of the expansion pipe!) and have the bike together again but I cannot get it to start! I've tried the bigger power jets but it can't be that anyway, he engine isn't even starting. I've checked the spark and it's fine, sparking away merrily. The float bowl is filling with petrol so it's not a feed problem, I'm thinking maybe low compression or a problem with the primary stage jets? Any ideas how to check? I don't have any equipment to check the compression, will have to take it to a mech for that, but before I go there can you guys think of anything I could try regards the carb? Link to comment Share on other sites More sharing options...
NEV Posted November 18, 2012 Share Posted November 18, 2012 Maybe some help with your paint coding Consmos, as you know Yamaha had a few different variants on their Blue paintwork schemes, but your colour code for the Blue on your 2004 bike is, Deep Puplish Blue Solid e (0583) As for the carb, I'd be inclined to whip it off again and give all the jets a good clean with carb cleaner, and a very thin piece of wire just to make sure, check the Gauze filter that sits inside the petrol intake spigot on the carb, a fair few people miss this filter, as when they disconnect the tank petrol tap hose they disconnect and leave the hose on the carb, unaware theres a filter where the hose attatches to the carb. Compression testers can be bought from Ebay etc, for around £15-£20 ball park figure, always a useful piece of kit to keep in the tool box, with testing yours should be around 95-100 psi, is your Airfilter cleaned and primed with 2t oil? also try a new plug, I'd bang an Iridium plug in, very good long lasting plug, giving a stronger spark too, in my opinion. Link to comment Share on other sites More sharing options...
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