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

[ash.onmtb]

Thanks mate, I've found these from DHZ

NEW MIKUNI CARBURETOR SLOW & MAIN JET KIT - eBay Other Makes, Bike Parts, Motorcycle Parts, Accessories, Cars, Bikes, Boats. (end time 08-Aug-09 11:23:55 AEST)

And they should do the trick, but the question remains... To go larger, or smaller...!? Or do I reset everything and try again?

With the symptoms present, does anyone have any idea?

 

[ash.onmtb]

actually, to anyone who's following this thread, maybe you can help?

I woke up this morning with a thought. When I stripped the carby, I strugged to get the bowl gasket to fit, it seemed to be oversized to the actual bowl. I did manage to get it carefully all stuffed back in as I tightened the bowl back on, but I'm wondering if the bowl doesn't seal, would that be allowing air in and leaning out the bike?? (if indeed that is the actual problem...)

If thats the case, does anyone have a trick to fixing that. The gasket is as good as I can get it, so if its leaking the gasket is not good enough. I'm assuming the carby is a mikuni 26 (copy most likely).

Jets should turn up next week sometime, hopefully I'll have this major issue sorted by then, and the jets will be a simple matter of tune.

Please help, I get sick of pulling the damn carby off so if I can get some thoughts before doing it yet again, it would be appreciated.

 

[thump*140]

Thanks mate, I've found these from DHZ

NEW MIKUNI CARBURETOR SLOW & MAIN JET KIT - eBay Other Makes, Bike Parts, Motorcycle Parts, Accessories, Cars, Bikes, Boats. (end time 08-Aug-09 11:23:55 AEST)

And they should do the trick, but the question remains... To go larger, or smaller...!? Or do I reset everything and try again?

With the symptoms present, does anyone have any idea?

Mate contact Ken at DHZ directly, (can be done through ebay site) and explain to him your problem. He is absolutely brilliant to deal with, and very quick to help. If you let him know the problems your facing, and enquire about a jet kit, he may be able to help with jets on the higher and lower than what you already have. This will allow you to try both, and this should give you an idea of which way to go... richer or leaner..
The gasket on your float bowl "shouldnt" suck any air if it's not aligned properly. you will soon know if it isnt right, as fuel will seep out of the bowl.. a bit of a trick for them in the future, if it gets fuel on it, they expand, which sounds like what you experienced... so if it happens again, dry it out a bit, and it will shrink back.. Dont dry it out with a cigarette lighter though.. ha ha

The other thing i thought, is that the carby itself may have coughed in it's nappy.. i experienced similar problems with the mikuni in my Thumpstar Hunge-ten.. ran great for ages, then one day just decided not to work anymore. Nothing on the bike had been changed, the jetting was as delivered and was jetted perfectly.. but something died in the carby, it's been cleaned, rebuilt, rejetted, all the tricks, and is still shagged.. Just a case of a cheap copy item failing... which may be the case with yours if jetting still doesnt fix it... keep in mind you did set fire to it...
... and no disrespect taken.... it helps if other people offer more ideas, more chance of finding the answer.

 

[DvDRip]

it's a genuine mikuni 26mm that's sold as a 30mm on egay, that doesn't make it a good carby, it sucks. I've got the same problem with the gasket being way too big on mine but found once you stuff it in there it's fine.

it's a prick of a carby to tune with the fuel screw hidden away underneath and the idle screw on the back.

 

[thump*140]

buy a 26mm oko flatslide. he he!

 

[thump*140]

just a thought... someone mentioned (MickCR i think) oiling up your air filter, and using plenty of oil...
did you do that? Too much oil will more or less starve the engine of air... look at it this way... try sucking air through water, without a straw...
if your filter is chock full of oil, that may be your issue... try the bike without the filter at all. if it runs happily, over-oiling the filter could be contributing..
oh, and the Mikunis have air passages on the filter side, at the bottom of the carby throat. it's not possible as far as i know to get into these properly to clean them out... when your carby caught fire, is it possible molten plastic/filter got into these passages? if it is the case, new carby might be your best bet...

 

[ash.onmtb]

nah, new filter, with only a bare minimum of oil on it as its just being ridden, umm, locally? It'll get a good oil before it gets used in anger.

Will tear the carby down again and reset everything to where I know it was right (ish...)

See what happens then..

 

[ash.onmtb]

fixed it...!

So all I did was drop the clip back down to the bottom of the needle, and its back to better than it was. So what I think I'll do is go up a size in main jet, and move the clip back somewhere near the middle so I've got some adjustment. I wonder how much better I can get it to go???!

So its got #100 in is, and I'm getting a 102.5 in the mail from DHZ - anyone care to guess how many notches back up the clip I can go? Prior to that, I can get a plug chop done on the weekend thankfully, so I'll be able to really see whats going on.

I wonder if I need to fiddle with the pilot jet...?! I wonder if the thing will go any harder than it already does.. So many questions, so little time to ride

 

[thump*140]

If moving the clip one or two notches on the needle makes a difference like that, "theoretically" it should mean your main jet is very close to being bang on... and if you've effectively raised the needle, thus richening it up, a #102 main should be pretty bloody close.
I'm taking bets that you will have to go back to either having the clip on the middle groove, or the one above... heh heh...
as for whether you need to fiddle with the pilot, what's the throttle response like off idle? if it's relatively crisp, well, if it aint broke etc etc..

 

[ash.onmtb]

Yeah, pilot should be fine me thinks. Will go up one size in main and try the needle in middle, after I see how the chop goes...

Happy to have it going again, thats for sure. Its a little fluttery through the midrange, not as crisp as I would have hoped. Perhaps a larger main and some tinkering will bring that into line, but a good run will probably help just as much.

thanks for the help.

 

[lvn]

i recon before u go any further buy a new spark plug and try that, ive redone my carby, checked my piston rings and tightened my valves all for nothing because my spark plug went faulty along the lines somewhere. just because it sparks doesnt mean its not buggered.

just thought ide go with another idea

 

[lvn]

never mind, didnt read everything and u fixed it, nice work