Oops I did it again, she played with my heart, Lifan 140cc

[Blender]

It should mould to the shape of your exhaust outlet, the one I put on my 125 leaked for a bit, but after every ride or so I would gradually tighten it up.

 

[gottagetacheaperhobby]

i have never got the flange to sit flush against the head, even when tightened right down. from memory, every engine i have put new copper gaskets in, have had the flange around 3 to 5mm from the head. provided the end of the header is crushed into the copper ring it should seal nicely. did you start the engine when you fitted it?

 

[Rikchick]

i have never got the flange to sit flush against the head, even when tightened right down. from memory, every engine i have put new copper gaskets in, have had the flange around 3 to 5mm from the head. provided the end of the header is crushed into the copper ring it should seal nicely. did you start the engine when you fitted it?

Yeah I started it, but it wasn't running too good, prob cause I'll need to try re-tune the carby, and then the carby started overflowing also..... Figured it was cause the flange wasn't sealing off properly, but perhaps it's all just because the carby needs adjusting again....


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[IAMTG]

The flange should not sit against the head. The idea is it pushes the exhaust into the gasket and crushes it somewhat to form a seal between the exhaust pipe and the head. The flange is only holding the pipe in. If you were to have the flange up against the head you would risk the gasket not sealing enough.

As for studs, get a couple of 8.8 tensile bolts at least as long as the current studs and cut the heads off with a grinder. Don't use a hacksaw as tensile steal will blunt half of the hacksaw blades you get these days. You should be using tensile 8.8 or 12.9 as they tend to get over tightened quite often and the last thing you need is to shear a stud at the head. Best to use tensile studs and stainless nuts that way your weakest point is the NUT which can be replaced easily.

Once cut off then lock 2 nuts together and screw the stud into the head. Dont forget to tidy the thread where you cut the head off the bolt.

 

[Rikchick]

The flange should not sit against the head. The idea is it pushes the exhaust into the gasket and crushes it somewhat to form a seal between the exhaust pipe and the head. The flange is only holding the pipe in. If you were to have the flange up against the head you would risk the gasket not sealing enough.

As for studs, get a couple of 8.8 tensile bolts at least as long as the current studs and cut the heads off with a grinder. Don't use a hacksaw as tensile steal will blunt half of the hacksaw blades you get these days. You should be using tensile 8.8 or 12.9 as they tend to get over tightened quite often and the last thing you need is to shear a stud at the head. Best to use tensile studs and stainless nuts that way your weakest point is the NUT which can be replaced easily.

Once cut off then lock 2 nuts together and screw the stud into the head. Dont forget to tidy the thread where you cut the head off the bolt.

Cool, I've just used some stainless bolts at the moment with spring washers, but that sounds like a good idea to make some studs from the bolts, will have a crack when I get a day off..... Erh work......


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[gottagetacheaperhobby]

you may find you even have to re jet the carby now if you tuned it while the exhaust gasket was leaking/not there, which ever the case was that caused you to replace it

 

[Rikchick]

Hey guys, so it's been a couple of weeks since I've had time to work on the bike, I've spent the day putting new studs into the head for the exhaust, the copper gasket is in, and I have tightened it all back up..... I then spent the next 4 hours playing with the carby tuning it. My biggest problem I have now, is when starting the bike, regardless of how the tuning is set on the carby, I actually have to turn the throttle for it to start, and (I think) because of this, I am having trouble keeping it idling. Unless I'm on the throttle it just does constantly. I was pretty happy with the carby mix, so took it for a quick spin down in the paddock, while negotiating some particularly slippery muddy spots, I was just trying to Coast thru in first, and it cuts out.... Every time I was in 1st gear off the throttle, it would cut out.

So it's ok when it's warm, and not under load, but whenever under load, it wants gas..... What else could this be, could it be the throttle needle position or the cable?


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[my67xr]

blocked pilot jet ?
or look into where the pilot jet screws into the base of the carby, check that the tiny hole at the bottom of the threads is open, and you can see light through it into the main bore of the carby

 

[Rikchick]

That's what I was thinking but it's all clean and clear, that's why I was looking for something else....


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[my67xr]

what about the port that lets the air through to it ?
did you blow them all out with compressed air ?
and what size is the Pilot jet in it now ?

 

[Rikchick]

Yeah, the ports are all clear, spent ages blowing air thru every hole I could find

The pilots got the same one in it, as the one I ordered didn't fit, it was a different type, and can't find any that are even similar.....

I'm over it, I think I'm going to hit up IAMTG for his carby he has now he's got a newie..... Just gotta see when I'm heading to the Gold Coast next.... Maybe Wednesday


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[my67xr]

can you put up a pic of the incorrect Pilot Jet ?
what were the differences to what you need ?
i might have the right one here i can post to you

 

[Rikchick]

Oops forgot the last pic

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There's the pic, my jet is at the top, and the #25 mikuni pilot is the one at the bottom....


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[stoozo]

Air leak in manifold or something?

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[my67xr]

that Pilot jet looks like someone has modified an Keihin/Oko jet ?

does your carby have any brand on it ?

 

[Rikchick]

Yeah it's a Jinke

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[Rikchick]

Hey guys, so, finally I bit the bullet and grabbed IAMTG's off of his mikuni and put it on my bike, little bit of tuning, and a new uni filter, and she bangs! I FINALLY have a bike that will idle, and run without bogging down, and is not popping and spluttering at every opportunity.....

So in the spare parts bin with the Jin Ke and out on the dirt for me tomorrow

I was so keen to put the carby on my bike, I only got home from work at 7pm, fired up the bike, tuned it, and took it for a little spin up and down the street (much to my neighbours displeasure I imagine) to test it! Yahoooo..... I have no words.

Many, many thanks to everyone who has helped with advice on this bike and especially to IAMTG for his help and awesome little carby!


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[my67xr]

good news !

 

[Rikchick]

Ok, so been out riding my bike all day, finally it's running and idling well, except....

It occasionally throws out a large pop when idling, so I tried tightening the exhaust bolts and checked all the manifold bolts were tight and no air leaks..... Seems all good..... Still popping....

Noticed that when I was riding, it hasn't once popped when in 3rd or 4th gear, running at high speeds, but almost always when I drop back into 1st or 2nd it will throw out a large bang.... I'm not sure if it's a "backfire", and definitely not sure whether it is exhaust related or carby related.....

So I thought I'd richen the mixture a tad on the carby...... Made all the popping worse...... Much more consistent pops, when I lean it out the pops reduce, but are still there..... I would have thought if it was pulling too much air I would need to richen it.....

So any more ideas would be good...... Also I have to say.... My exhaust pipe and muffler probably aren't in the nest condition, they are pretty rusty and I haven't re packed the muffler at all..... Could this be the issue?



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[stoozo]

To rich dude!! Sounds like you need to go out half a turn out your mixture screw?! Def backfires....to much fuel going undetonated into the exhaust thats why its backfiring!! How is it looking where the exhaust and muffler join?

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