Hey gents, I'm after a bit of carb info if possible.
I have an '03 DTR with a Big One expansion and afaik everything else is standard at the moment.
When I had a look in the Haynes manual for the bike, it states that the main jet size is supposed to be a 240, on the standard mikuni carb anyway.
I was under the impression that the 240 jet was an upgraded size until I read this.
Any ideas folks?
Also, when the bike has been derestricted, should you mod the airbox at all? Like bigger snorkels etc. As an experiment I removed the side panel and the air filter and ran the bike like that, the throttle response instantly improved, and I can't help but think that the airbox needs to be modded for a better performance?
All ideas/suggestions/advice appreciated!
Cheers
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on mine iv taken the snorkel off, upjetted (for dep pipe jet size recomended from yam dealer, cant remember size tho lol) and pv pinned open, im running standard exhaust non-gutted, n mine runs like a dream
I'll have a chat with my Yammy dealer then, see what they reckon the jet size should be, cheeeers fella!
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The 2003 DT125R DE-RESTRICTED jet size is a 260. This is a mikuni jet size, and is not to be confused with other carb manufacturer jet sizing!
I have spoken to a Yamaha dealer this afternoon who recommended this size, and also recommended running for a few miles and doing a plug chop to make sure :)
-- Edited by mammoth200 on Friday 18th of March 2011 04:50:51 PM
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
I've heard you can drill holes in the side of the airbox to increase the amount of air going in, upjetting would be necessary for this I would assume. On the other hand i've heard this is a bad idea as it only provokes the bike into bogging down, this is what i thought you were going to say...but obviously you got the opposite haha which is strange cause even with the snorkle removed on mine, throttle response doesn't feel as sharp...sounds nicer tho
My bike has been drilled the air box, coverdd it up as good as i can , and brought a stonkel that has been drilled.But not it ticks over, and stats with out choke when got , and doesnt bog so much
Well it always better to be running rich rather than lean, and yeah its definitely a 240 in there at the moment, as I actually whipped it out and changed it for the new one, when I opened the carb up I found a 240 already in there, but changed it for a new and clean one anyway. I've got the new one coming hopefully monday, 3.50 on ebay :)
My mods after a top end rebuild should be:
1) Aftermarket Big One Expansion and DEP endcan 2) Snorkel either removed or revised 3) Reed block internal rubber removed on the inside 4) screwed on bottle on the side attached to airbox blocked off 5) 260 main jet fitted
This also includes the restriction in the speedo which I have already sorted!
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
Right! I have yet to do the top end rebuild on my DTR but all other mods have now been completed, starts up, runs fine and seems to rev better in the range, this is all in neutral however, so I'm gona run to work on it in about half an hour, and I'll post results either tonight or tomorrow!
The mods are as listed above!
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
Modifications are a complete success! The improvements are massive! It revs freely and far faster throughout the rev range, warms up faster, and pulls like a train! Of course I'll probably find out that I've lowered the life of the rings and my mpg will be worse, but imo it's well worth it, it really irons out all the niggly little problems I had when accelerating :) I'll do a full report tomorrow when I'm on my comp as opposed to my iPhone lol
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Hopefully if the piston rings turn up over the next 2 days I'll be able to get an 'after' pic, I didn't get a chance to take any today as my time was limited, I'll see if I can find an original pic of the manifold as stock.
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
The modifications are quite straight forward, its obviously just a case of having everything apart. I'll start with the easiest of the two.
1) With the mod on the airbox snorkel, all I did was remove about an inch with a stanley knife, this is easily do-able. What you are left with is the bend and a 50-60mm long snorkel underneath the seat. I can take a picture if necessary but its straight forward enough not to need one imo.
I'm not fond of the idea of completely removing the snorkel. It's never worked well for me in the past, not on a 2 stroke anyway. All I have found is you have to overcompensate the fuel mixture for the extra air. Some folk have a tendency to forget that when one is vastly increased, the other needs to be as well. with just trimming it down you are set up correctly for a 260 jet :).
2) Next is the screw on bottle on the side, all you need to do is remove the bottle, and block the hole. Very easily done with a square of duct tape, make sure it folds over the edges on the bottle, you don't really want it being sucked through the carb! All you need to do then is push the bottle back on, and screw it back on to the frame.
3) Now, to modify the inlet manifold, remove the manifold from bike (obviously) and the basic idea is to remove the rubber chunk that slots inside the reed block, as per the drawing. You need to be careful here as there is a raised edge that goes around the outside of the rubber insert, you don't want to cut this as its a sealing edge! What you want to achieve is a completely flat profile, apart from the previously mentioned raised edge. I'll get a picture of this for anyone who may be interested, but it wont be until the weekend. Re-fitting is the opposite of removal!
4) I won't explain how to change the jet in the carb, unless you want to know, in which case just ask, and i'll post a how-to. But basically you replace the 240 jet with a 260. All I will say is when you put it all back together, make sure you allow enough time for the float chamber to re-fill before you try to start it, patience is a virtue!
And thats it really! The bike no longer hesitates at 7000rpm, its made the throttle response much sharper, and it just generally feels much more up to the task! I will state that the gains I have discovered are for a DT125R '03 model. The other models may differ! If you chose to take a stanley knife to your bike, thats your perogative, i've given a guide on how to do this, but don't point the finger at me if something goes terribly wrong! Not that it should.. jus sayin... lol
You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
Top end rebuild should be happening today! I'll try and be as pic happy as I possibly can, I'll also get a picture of the inside of the reed block too. Might be able to get enough pictures to do a top end rebuild guide for any newbies!
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
Well today turned out to be more interesting than I expected! Got the bike stripped down, cylinder off, went to fit the new rings... Didn't match the piston! Turns out for some reason the standard rings don't fit my standard piston? No idea, either way, I had to take a little trip to Ipswich with my barrel and weirdo piston, to get a shiny new Mitaka piston. So much for my ban on buying shiny new bike parts this month... lol.
Had a bit of luck when I got to the engineering place, the chap there asked if I wanted the cylinder honed and given a hot bath to clean all the **** off? I said yes. Of course. And it only cost me a fiver! Did it whilst we waited!
Eventually got back to my dads at around 5 o'clock, beginning to run a bit shy on daylight so I never had the chance to take photo's of all the shiny new parts going back in. Did manage to get a picture of the cylinder head after being cleaned and lapped, and also took a couple of 'before' pictures. Weather permitting I'll get a couple of pics tomorrow, even though the engine is back in one piece lol.
Had to take it gently on the trip back home from me dad's, its only about 10 miles, Didn't go over 6000rpm the whole way, it was a slow journey in 6th gear at 40mph, I hate running in!
Any consensus on running in procedures? I plan to go easy on it until I need to fill up again, so about 70ish miles.
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
liking it m8 iv been runnin my new piston in just by letting the engine tick over in the garden then giving it some low revs every now an then for about a week. then took it out for a slow run a few times when i got the swingarm bolt, an let it cool right off before i went out again for 30 mins obviously it revvin like mad for no reason was a bit scary for the new piston so cheers for that info it helped a load m8. see you went to ipswich , i used to go clubbin there nearly every week when i lived in back colchester
good thread mammoth im gonna try n get hold of another inlet mani n doo that mod, i hav a manifold off a older/newr than what i got( has no 2t oil feed into it??) obviously i cant run that mani but it doesnt seem to have such a big chunk in the inside it looks quite free flowing
To be honest I would have thought that was from an older model, possibly one that either runs the oil through the carb, or a pre-mix set up, maybe an official dirt bike, YZ etc. It's easy enough to imagine the difference, if you were to remove those two rubber peaks, you would essentially have what I am currently running. Although I would imagine you'd get a pretty good response from the engine if you could rig that one up, it has a much wider profile.... Probably set up to run 34mm+ sized carb? Have you tried to fit the DTR Mikuni 28mm standard jobbie into it?
EDIT: after a quick investigation, thats a TZR manifold!
-- Edited by mammoth200 on Sunday 27th of March 2011 12:41:08 AM
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
I'm not sure, logically it should have some effect, but from my perspective, top speed was never really a concern, I much prefer to have fast accelleration. I don't mind if my bike only does 70mph, because in all honesty, that's essentially as fast as we are 'allowed' to go.
But if I get there in less time... that's good :)
Anyway, when I've run my new top end in, I'll smash the nuts off it and let you know what happens!
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
Finished work at 2:30am, went outside, started the bike up, everything was fine, got to the other side of the car park and it died. Not started since :( so I had to push the f*cker home. Not happy! I have a feeling she's running rich, and in doing so I've killed the plug. Alternatively it might be a fuelling issue.
My mission tomorrow is to make sure I'm getting fuel air and a spark. Joy, I hate it when bikes do this, especially after I've just rebuilt the top end! Makes you think somethin baaaad has happened...
I'll keep you peoples posted.
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
It ate the plug! Must have been because it was running rich. I've whipped out the snorkel as well, gona put some fine mesh over the top of the hole to stop the **** getting through. I'm keepin you updated!
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
Just a final (hopefully!) update, I have since removed the snorkel from the airbox, and covered the hole with a nice chunk of wire mesh, to stop the sh*t getting in there.
I have also run the bike in now.
JESUS.
She goes like f*ckin stink! Eats up the rev range so much quicker than she used to! I reckon I could probably get the front end to lift if I dumped the clutch fast enough, with no other encouragement :) I'll have to do a plug chop in the near future, just to make sure she's not running lean, but its a huge improvement in comparison to before I rebuilt it! Weather permitting, I'll do a compression test tomorrow, hoping for good high numbers :)
I think my next mod will be a 3MB cylinder head, with the improved squish!
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
