Jetting the carb

[Calum]

Well, the Mito engine is highly strung. The Mito runs rings around the DTR, but as a result they're a lot more fragile.

I had the same thing with my ETX, absolutely battered bike, but it's in such a low state of tune that the engine was crisp, almost criminal to rebuild it.

[Elan n]

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[Elan n]

@calum @hotshot-iii okay a lott happened in the meantime. Firstly i fixed the servo cables and after cleaning procedure it aligned perfectly with the hole. Looked in the exhaust port and was correct. Removed the spacer but kept the carbon reeds. Still runs like crap en servo moved weirdly, not correct in my opinion. That aside, still stutters right before powerband. With as well the 210 and 17.5 jetting and 240 and 27.5(French setup )but with the higher jets i had a lot better throttle response and idling. With the richer setup i tried it to pin the pv on the open position to see what it does when i hit the powerband. And finally it hits but only in first year tho :s the other gears is starts stuttering again.
Checked my deristrictrion and everything was like its supposed to. So yeah im out of ideas now haha, i run a br9es also like im supposed to. Checked for air leaks, no leaks present. Cleaned air filter and oiled it correctly. Also of i compared the original mikuni jet 210 with the new 240(also a real mikuni) the hole on the 210 was bigger??

[Calum]

So I don't align the powervalve with the hole (partly because my exhaust/valve have been ported so it probably isn't right anyway. You did right by aligning flush with the exhaust port. I'd just focus on that, take the exhaust off and align it with the exhaust port. Flick the ignition on and off a few times to make sure the cables don't realign.

If you want a quick way to diagnose your problem to get you a steer in the right direction then I'd do this.

1. Align the powervalve flush with the exhaust port
2. Disconnect the powervalve servo
3. Remove the carb air filter boot (eliminating the airbox)
4. Run the bike with no air filter

What this should do.

Remove the powervalve will stifle bottom end, but 6k+ should shoot off like a rocket.

Eliminating the airfilter removes any restrictions that might be present in the air intake tract. Whilst not ideal running without a filter, it will be fine for a short space of time. Unless a stone flicks into the inlet you'll be fine.

You should now be running the bike quite lean (so avoid prolonged wide open throttle). The bike should run better now than ever.

If it runs worse, it tells you your jetting is too rich. If it runs better then you know that you need more fuel. If it runs the same, then you know the problem lies elsewhere.

I am expecting it to be the latter, I'm expecting the problem to lie else where, but ruling these items out first, means we can then start to go more technical knowing that we've addressed the simple things first.

[Elan n]

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[Elan n]

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[Elan n]

@hotshot-iii @calum im so angry at my self , the hole time the problem was that i drove without the seat so my butt was too close to the snorkle. Went from 17.5 to 27.5 and 210 to 240 and runs like an angel. The 210 was totally worn out and was bigger than the 240.
Both are genuine mikuni jets btw. Still changed the coil tho. Threw that Chinese orange coil in the bin

[HOTSHOT III]

@Elan-n Don't worry about it, I've done a lot worse! Sometimes you can be so close to the thing you're trying to fix it's easy to miss something. The main thing is you're moving forward

[Elan n]

Hey @calum @hotshot-iii i already have a blast on de dtx. Currently running in 27.5 pilot, 5j40 needle with clip on the leanest. And a 240 main. It works very wel. Only 50/50 times it sputtert right before the powerband and somethines within. If i go full throttle from the start it stutters more often and if i give half throttle and when it hits powerband to full throttle it pulls al lot better. Other times it pulls straight forward like a beast. Did a plug chop on full throttle and sparkplug is on the brown side but not wet or anything. It has also a little struggle in sixth gear to get higher rpms around 100km/h Any tips?

[HOTSHOT III]

@Elan-n Considering your symptoms the only thing I can really think of is incorrect float height; the only reason I'm suggesting this is, Haynes made a big mistake and got their VM26SS (round slide '88) float height (21mm) mixed up with the later TM28SS which should be 15.5-16.5mm. A lot of people read this and through no fault of their own, set their TM28SS float height to 21mm which of course means there's (a lot) less fuel in the float bowl at any given time. This could explain why the bike's pulling well when you wind on the power gently, but struggling when you apply full throttle straight away. Appreciate the plug colour might reflect a lean running condition but on the other hand it might not if you're experimenting with a lot of different engine speeds/throttle openings as a plug chop is only of any real use when done precisely at a specific engine speed according to a lot of two-stroke tuners.

Other than that, intermittent problems are often something simple; I'd go right through the electrics and clean up/WD40 every connector for starters. A corroded block connector somewhere can throw up all kinds of head-scratching like this. Do the handlebar switches, sidestand switch and the electrical part of the ignition switch (these usually have small hole for this purpose) as well, really blast the WD40 in so it fizzes and bubbles out of all the gaps and flushes out the corrosion as the exposure to all weathers on a bike is a harsh environment for a switch. Throw old towels over the wheels while you do it to protect the tyres and brakes.

I once lost the spark altogether on all 4 cylinders of a Suzuki GSF400 Bandit, it was a Japanese import with complicated V-Tec variable valve timing and no service information available in the UK so it caused me a measure of panic as you can imagine. The parts guy at the local Suzuki dealership simply said "a set of plugs (£10 each in 1998) will get it going". I thought you've got to be a genius to make 4 NGK plugs fail at exactly the same instant and so declined his offer. A bit later I was cleaning it and saw a relay under the seat (I still to this day don't know what it was for, poss. sidetand switch-related or something) which had some blue copper sulphate-looking corrosion oozing out of it, so I cut it open with a small hacksaw and found one of the tracks in the PCB had corroded through. Half an hour with the soldering iron, I bridged the split with a tiny wire out of one of those 8-pin landline phone connectors and it started up and ran perfectly.

You're going in the right direction with this, if it runs really well some of the time I don't think its jetting related.

[Elan n]

@hotshot-iii hey, before assembly i adjusted the float height to 16-16.5mm according to the maintenance manual. I went through all ignition related cables and switches but nothing out of the ordinary. No corrosion etc... Also installed a genuine replacement coil and measured the primary and secondary winding just to be sure haha. The plug chop was done at 10k rpm. Did it a lot with mopeds to check if the main jetting was right. Today it was less hesitant to pull through so it went better when i just gave it full throttle from the go. This was after i finished the idle configuration with the screws. Steady +-1.6k rpm like the manual says and the air mixture screw is just about right. Temperature is very stable +-70 degrees celcius and its stay like that after driving almost an hour long. Im suspecting 2 things that are happening, correct me if im wrong haha. 1st thing is my powervalve that is opening a little bit to slow, i feel if they once open up, i can hear it and feel it and i can give them beans without any problem. Tohe other thing is maybe im running too rich in the lower rpms?