To the carby guru's - what are the chances?

[ash.onmtb]

To the carby guru's - now what have I done??

So last week ya'll might have seen about burning off a filter in my PP140.

I got a new angled unifilter from East50's (top service!) and whacked it on today. Kicked the thing in the guts and had a roll around the locaaaaal. A little while after getting it going (doesn't start real flash...) it started to get a bit miserable. At a frisky idle, the thing will pop and backfire very regularly, and even winding the idle screw almost to the stops will still not allow it to keep running, it just slowly dies...?!

My thoughts are this. After burning off the carby, I still had to ride it a few hundred metres back to the truck, and I'm contending that its slurped up some of the burnt residue and gotten it clogged somewhere?! The bike still happily goes like stink on the throttle, but at idle its not possible to let go of the throttle without it stalling out, and at a fast idle the thing is popping all over the shop. Also on over-run or when rolling agains the engine, its popping and backfiring all over the shop.

What do you reckomend I do. Everything is stock thus far. Mikuni 26 (stamped on manifold - says 30 in the paperwork)

What to do??!

thanks.

 

[coolmodee01]

valve clearance ^^^^^^ bent valve nay have been what caused the fire

 

[headsmess]

^^^^^im with coolmods


i am not writing it all out again, how to check valves quickly...

right click search, open in new tab

 

[motovert24]

change everything to the high qualty [ better carby and stuff like that and what coolmode said] or get a new bike

 

[DvDRip]

yeh I'd do a leakdown test on the intake valve, stuffed valve is the only way I can think of that would make it backfire through the carby

 

[dhz140cc]

lol motovert wtf are you on about..?? get a new bike cause it has a bit of carby problems.

 

[motovert24]

don't get a new bike but fix the one you have is it a pit pro and how old is it

 

[headsmess]

ok, cus im very bored....i shall rewrite everything, in abbreviated form

remove rocker covers. find TDC on COMPRESSION stroke(once inlet valve has gone down then back up, flywheel mark T at 12oclock)..... give both rockers a wriggle(vertical, up n down, not sideways.......) almost guarantee therell be no clearance on either of them...

.004/.005 IN/EX... or 0.1mm approx... not much... but more is better than less... up to a point...

next...if there IS clearance....leak down test... pour some kero into the inlet port til its full... walk away... if levels dropped SIGNIFICANTLY(a few mm) after half an hour, its a leaky inlet valve...quick drain? bent valve... or slow drain? needs reseating/grinding.....remove plug and kick over a bit to clear the kero out...

failing these simple tests, then the problem lies elsewhere...or the exhaust valves screwed... can be tested much the same way as the inlet, but filling the cylinder at TDC,compression stroke, no plug... and maybe oil instead of kero...anything to avoid tearing the head off for no point...

theres nothing wrong with the carbie(we hope), and any bikes better than mineexcept....mine doesnt catch on fire

 

[mickcr250]

did you have your filter properly oiled? if not this could be the reason it caught fire, it might also be why your bike is running poorly. australia has some of the finest dirt in the world and it is important you put plenty of oil on your filter. you probably dirt in your pilot jet witch will make it run poorly at low rpm. take the carb off, remove the bowl, float and jets and clean it all out with carby cleaner and blow threw the jets with compresed air. make sure you are very carful and keep everything really clean it doesnt to block up a jet.

 

[pbk]

^^^good call mickcr

do your valves first follow headsmes instructions

then if that dont work strip your carby and clean your jets right out and your fuel bowl may have some crap in it too

 

[ash.onmtb]

So I did some digging today and found some things out.

Valve clearances that I found to start with: About .002 on intake, .005 on exhaust, so put them at .003 intake, .004 exhaust to learn how to do it if nothing else. What a PITA that is...

Problem of crap idle was still apparent, couldnt even really get it to idle without excessive idle screw movment. Popping and backfiring, bogging down a bit if rough on the throttle, so generally crap.

Pulled the carby off (first time). Moved the clip up 2 notches for no real reason other than to see what happens, as it was at the lowest mark. Pulled everything apart in carby and cleaned, then blew out. Rebuilt and tested and problem *seem* to be gone. There was some grit in the bowl so I contend it got into the slow circuit/20 jet and was being annoying.

So it comes with a 100/20 jetting. I need to do a plug chop to see where its at, but the valves have reduced the noise it was making (from out of the box so i never knew any better), and I need to ride it a bit more to see if its all better. I think its just a tuning thing to get it hummin now - the fuel screw ended up being out about 1.5 turns for happyness to prevail.

How's that sound, like I'm making sense??

 

[pbk]

making perfect sense good to see you picked up on it all fairly quickly

 

[pooley770]

but when u oil your filter dont make it rich in other words put to much on as it can tend to make things play up

 

[thump*140]

So I did some digging today and found some things out.

Valve clearances that I found to start with: About .002 on intake, .005 on exhaust, so put them at .003 intake, .004 exhaust to learn how to do it if nothing else. What a PITA that is...

Problem of crap idle was still apparent, couldnt even really get it to idle without excessive idle screw movment. Popping and backfiring, bogging down a bit if rough on the throttle, so generally crap.

Pulled the carby off (first time). Moved the clip up 2 notches for no real reason other than to see what happens, as it was at the lowest mark. Pulled everything apart in carby and cleaned, then blew out. Rebuilt and tested and problem *seem* to be gone. There was some grit in the bowl so I contend it got into the slow circuit/20 jet and was being annoying.

So it comes with a 100/20 jetting. I need to do a plug chop to see where its at, but the valves have reduced the noise it was making (from out of the box so i never knew any better), and I need to ride it a bit more to see if its all better. I think its just a tuning thing to get it hummin now - the fuel screw ended up being out about 1.5 turns for happyness to prevail.

How's that sound, like I'm making sense??

your jetting sounds pretty close.. Maybe a little smaller on the main jet, might clean up the bogginess when you crack the throttle, seeing as you already done the needle... Too big a main jet, will also effect needle jetting to a point... the other thing is, it takes very very little grit in the bowl to block the needle... seems that one grain of sand will suck into the needle jet when the needle rises, blocks it partially, makes it run crappy, then drops out again when the needle comes back down...tricky.. your air screw adjustment sounds pretty right too, 1.25 to 1.5 turns out is usually spot on...

 

[ash.onmtb]

alright, now I'm confused.

hopped on the bike to ride it around the yard for a spell, and its gone all weird...

Full choke - idles awesome, toey off the line, bog's bad at half throttle
Mid choke - idle good, doughy off the line but bearable, runs out of puff very early and sounds like the choke is on (full choke I mean)
No choke - doughy as hell till it gets a a run on, then winds out slowly but not crisp by any stretch...

Its warmed up.

Everything is the same bar the fuel screw and the needle up two grooves...

What do I do to make this better... It used to work waaay better than this. On the plus side, it started way better than it used to

Is it too lean now??

 

[thump*140]

hmm... sounds pretty similar to what my 140 did when i first fitted the 28mm flatslide...
i'd suggest setting the clip in the middle groove on the needle, and find yourself a #92 mainjet.
Mine was the same... really toey off the bottom with the choke on, choke off and anything over half throttle was just fuelling up and dying...
if your motor is standard, i have a feeling your main jet is about ten increments too big, and is effecting your jetting on the needle... in which case no fiddling with the needle clip or air screw will have a desirable effect..

 

[ash.onmtb]

problem with that is I thought it used to go great..!?

What would change so much?! I tickled the fuel screw, and move the clip up two notches from the complete bottom where it was..!? Now its poo... So do I set it all back to where it was and see how it goes? One person says #105, another says #92 main jets.. Help!! I'm confuseled...!

I want the thing to go good, but I'm getting donuts. And I don't reckon a plug chop would even be possible in its current state of tune... (as in, getting it wound out top gear)

What now peoples?

 

[thump*140]

Hmm... Where's Mr Cactus when you need him....
without seeing or hearing the bike running, if it's worse with the needle set in the middle... hmm..than it was with the needle on the bottom clip... that means leaning it off made it worse... which theoretically means the main is too small... but you already have a #100 main in it... which is getting pretty big for a 140... kinda doesnt make a lot of sense given the jet sizes you have... the pilot jet is pretty small at a #20 too... the best suggestion i can make is to clean the carby again, (you never know how unlucky you can get with grit) and perhaps look at getting a spare jet or two...
I think, and hopefully someone can back me up on it, that you need a pilot jet closer to about #30-#35, and still contend the main is too big. Why not grab a #92, and a #105. Set the needle in the middle, and try the two different main jets back to back.. see which runs better... Keep in mind these are very small engines, and small changes in jetting sizes makes a big difference... put it this way... My Honda 750 Black Widow runs #135 main jets... engine capacity 6 times the 140... with main jets not a lot bigger... However, jetting is a black art, and if the OKO flatslides are anything to go by, symptoms can be the exact opposite of what's wrong... ie: your bike sounds like its starving of fuel... but i still reckon it's running rich... try a #92 and a #105 back to back. one of them is bound to be better than the other, and this will at least tell you which direction to head in... richer or leaner..

 

[ash.onmtb]

no disrespect to Thump, but anyone else got some ideas??

Or an ebay link to a set of jets that will work and I can try??

Thanks.

 

[pbk]

email dhz i just bought a couple off him today or what carb do you have??? you may be able to take the carb into honda moto shop or alike and they may have jets to suit