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Deece55
L Plate Warrior



Joined: 21 Oct 2010
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PostPosted: 17:38 - 21 Oct 2010    Post subject: kh125 jets Reply with quote
My d reg kh125 has recently had a big bore (due to damage caused by the autolube failing). It is now +1.5 on standard, and i need to find out how much i should drill the jets out by to ensure it runs balanced. Confused
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nowhere.elysium
The Pork Lord



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PostPosted: 21:39 - 21 Oct 2010    Post subject: Re: kh125 jets Reply with quote
Deece55 wrote:
My d reg kh125 has recently had a big bore (due to damage caused by the autolube failing). It is now +1.5 on standard, and i need to find out how much i should drill the jets out by to ensure it runs balanced. Confused


Right, well to countermand Esoteric1's ramblings, I'm going to offer the more appropriate (and fundamentally basic) advice: Don't Drill The Jets.

Buy some jets, and re-jet it with those by all means, but given that jets are typically measured in microns, do you honestly think that 1) you've got a drill bit precise enough, and 2) your hand is steady enough?

The most likely answer is no, to both of these questions.

Jets are cheap, and readily available. What's the carb size/make/model? Should have at least the make stamped on the side.
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serlant
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PostPosted: 21:40 - 21 Oct 2010    Post subject: Reply with quote
Esoteric1 wrote:
Just wondering why an expert hasn't answered your question yet?

Well the KH 125 is 125cc as standard 56.0 x 50.6 mm (2.2 x 2.0 inches).

You say it is now +1.5 on standard.

I could be wrong but to my logic this could mean either 125cc+1.5cc=126.5

Or + 1.5% of 125cc =1.875
125cc+1.875= 126.875, or to round this up 127cc

This means oversized piston kit and or rings have been installed. If this is the case then up jetting won't be required.

Was is the actual bore size in terms of cc or diameter?

Still wondering... Rolling Eyes I believe the 1.5 is MM oversize as for drilling the jets, just buy a bigger jet, i doubt you're going to to it any favours by best guessing it with a drill bit?
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SillyMe
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Joined: 11 Oct 2010
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PostPosted: 22:07 - 21 Oct 2010    Post subject: Reply with quote
Funny how loads of jump on the bandwagon doods jumped on this question after I answered it. It was asked hours ago and no else offered to answer the question.

Siily idiots asking people to die!
They have probably just finished work and maybe tiered.


What is the actual bore size in terms of cc or diameter?
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Owned and rode: Honda 100H, Honda MBX 125, Kawasaki AR 125, Suzuki RG 125 Pepsi, Honda NSR125 RK, Honda NRS 125 race bike, Suzuki GSXR 400 Bandit, Aprilia RS 125 O2, Honda CG125, Kawasaki KMX 125, Aprilia RS 125 O6, Suzuki XT225 and now Honda XR 400. ( A few scooters and other dead beats in between)

Last edited by SillyMe on 23:17 - 21 Oct 2010; edited 3 times in total
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SillyMe
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PostPosted: 22:49 - 21 Oct 2010    Post subject: Reply with quote
Edit!
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The man who says "I may be wrong, but -" does not believe there can be any such possibility
Owned and rode: Honda 100H, Honda MBX 125, Kawasaki AR 125, Suzuki RG 125 Pepsi, Honda NSR125 RK, Honda NRS 125 race bike, Suzuki GSXR 400 Bandit, Aprilia RS 125 O2, Honda CG125, Kawasaki KMX 125, Aprilia RS 125 O6, Suzuki XT225 and now Honda XR 400. ( A few scooters and other dead beats in between)

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chris-red
Have you considered a TDM?



Joined: 21 Sep 2005
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PostPosted: 12:07 - 22 Oct 2010    Post subject: Reply with quote
SillyMe wrote:
Just wondering why an expert hasn't answered your question yet?

Well the KH 125 is 125cc as standard 56.0 x 50.6 mm (2.2 x 2.0 inches).

You say it is now +1.5 on standard.

I could be wrong but to my logic this could mean either 125cc+1.5cc=126.5

Or + 1.5% of 125cc =1.875
125cc+1.875= 126.875, or to round this up 127cc

This means oversized piston kit and or rings have been installed. If this is the case then up jetting won't be required.

Was is the actual bore size in terms of cc or diameter?


Twat

1.5mm over size means the bore is 1.5mm more not the area.

CC is one cube centimetre not millimetre.

To get the area (cc of an engine.) pi x bore/2 ^2 X stroke.


2.8 x 2.8, (half the bore converted into CM and squared) x 3.14 (pi) x 5 (the stroke in CM) which equals 123cc which is what it was originally.

The extra 1.5mm on the bore means the new capacity is 129.7cc

a 6cc increase is not enough to bother the jets for let alone 1.5cc increase, Drilling them is ridiculous.


You said you where a qualified mechanic, I have never been on a mechanics course in my life and I know this stuff.

Stop posting shite.
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chris-red
Have you considered a TDM?



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PostPosted: 12:10 - 22 Oct 2010    Post subject: Reply with quote
SillyMe wrote:
Funny how loads of jump on the bandwagon doods jumped on this question after I answered it. It was asked hours ago and no else offered to answer the question.

Siily idiots asking people to die!
They have probably just finished work and maybe tiered.


What is the actual bore size in terms of cc or diameter?



Why would you answer if you don't know?

The bore a length i.e. 2 dimensions in in mm, the Capacity an Area 3 dimensions is in CC.
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Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.
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chris-red
Have you considered a TDM?



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PostPosted: 12:13 - 22 Oct 2010    Post subject: Reply with quote
A fucking qualified Mechanic not understanding the Basis of engine capacity Laughing



Quote:
What is the actual bore size in terms of cc or diameter?


This is pure gold right here.

The bore size IS the diameter the CC is an area.

Qualified mechanic my left bollock.
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Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.
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nowhere.elysium
The Pork Lord



Joined: 02 Mar 2009
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PostPosted: 13:46 - 22 Oct 2010    Post subject: Reply with quote
SillyMe wrote:
Funny how loads of jump on the bandwagon doods jumped on this question after I answered it. It was asked hours ago and no else offered to answer the question.


The point is not to post a steaming pile of lies to fill time while waiting for someone competent to turn up, the point is to give accurate, sensible advice.
Can you do us all a favour and just shut up?

Also, OP - to summarise:
Don't hand-drill jets, it always ends badly. See how the bike's running, and check the state of the plugs. If they look OK, and the bike's not got any significant flat spots, you don't really need to do anything much to it, other than ride.
If, however, it's running lean (as denoted by whiteish plugs), you'll need to rejet it as soon as possible, otherwise you face the prospect of holing the piston.
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Syris the Indomitable
Crazy Courier



Joined: 22 Oct 2010
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PostPosted: 13:53 - 22 Oct 2010    Post subject: Reply with quote
Well don't know what chris-red is on about showing how to calculate bore sizes. The KH is a standard 125cc, not 124 or 123cc.

Esoteric or what ever his name is already said
Quote:
This means oversized piston kit and or rings have been installed. If this is the case then up jetting won't be required.


Rob Rar was helpful. Why not allow the person who asked the question to over elaborate on what he has already asked.
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nowhere.elysium
The Pork Lord



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PostPosted: 14:05 - 22 Oct 2010    Post subject: Reply with quote
James smith wrote:
Well don't know what chris-red is on about showing how to calculate bore sizes. The KH is a standard 125cc, not 124 or 123cc.

Esoteric or what ever his name is already said
Quote:
This means oversized piston kit and or rings have been installed. If this is the case then up jetting won't be required.


Rob Rar was helpful. Why not allow the person who asked the question to over elaborate on what he has already asked.


Oh look, another sock puppet. Feel free to actually do some research: the KH125 had a 123cc engine, and it was called a 125, because that's the general class of bikes they wanted it to be synonymous with, just like the CG125 is actually a 124cc engine.
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chris-red
Have you considered a TDM?



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PostPosted: 14:42 - 22 Oct 2010    Post subject: Reply with quote
James smith wrote:
Well don't know what chris-red is on about showing how to calculate bore sizes. The KH is a standard 125cc, not 124 or 123cc.

Esoteric or what ever his name is already said
Quote:
This means oversized piston kit and or rings have been installed. If this is the case then up jetting won't be required.


Rob Rar was helpful. Why not allow the person who asked the question to over elaborate on what he has already asked.


Actually it is 124.5, I didn't add the .6 of the stroke


The engine size for the bikes is rarely what is is said on the side of the bike.

Most 600's are 599.

My mates 600 monster was 583.

My old RXS100 was 98cc.

1200 bandits are actually 1157 the list goes on.


If you look on the side of the barrel it will say exactly what size it is.

Now you do know what I am talking about.

The number is usually rounded up to something that sounds sexy.
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Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.
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Deece55
L Plate Warrior



Joined: 21 Oct 2010
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PostPosted: 17:43 - 22 Oct 2010    Post subject: Reply with quote
Oversize is measured in mm. As for drilling the jets i'm not quite nieve enough to try and do by hand! I have access to laiths, borers and milling cabinet's at work so can sort most things if know sizes.
Will check the carb numbers when get home in few hours. Hard to tell if running lean or rich at mo as using heavy tank mix whilst running in the new Piston and rings. Mixture was always ok before the piston melted to the cylinder, but bike ran weasy with flat spots all over, was +0.5mm oversized then so pretty sure will need jetting now!
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nowhere.elysium
The Pork Lord



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PostPosted: 11:04 - 23 Oct 2010    Post subject: Reply with quote
Deece55 wrote:
Oversize is measured in mm. As for drilling the jets i'm not quite nieve enough to try and do by hand! I have access to laiths, borers and milling cabinet's at work so can sort most things if know sizes.
Will check the carb numbers when get home in few hours. Hard to tell if running lean or rich at mo as using heavy tank mix whilst running in the new Piston and rings. Mixture was always ok before the piston melted to the cylinder, but bike ran weasy with flat spots all over, was +0.5mm oversized then so pretty sure will need jetting now!


Sorry - I wasn't impugning your intelligence, but we do get some real numpties on here, sometimes, as has been amply demonstrated my Esoteric1, or whatever he's calling himself now.

As I've said, you should be able to get jets cheaply - if you find out what the standard sizes are, buy a range of a few that are larger; at least this way, you make no destructive changes, and it allows you to fine-tune the fuelling.

If the piston melted to the cylinder, it's running horribly lean. I don't know enough about rejetting to be able to make authoritative statements about what jet sizes to get, but I can comfortably tell you that the difference in sizes is on a micron scale, so it's really not worth trying to do it yourself, regardless of the kit you've got. Also, as I've said, destructive changes like drilling are pretty hard to undo.
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Syris the Indomitable
Crazy Courier



Joined: 22 Oct 2010
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PostPosted: 13:09 - 23 Oct 2010    Post subject: Reply with quote
Eso! already told you this.
Quote:
This means oversized piston kit and or rings have been installed. If this is the case then up jetting won't be required.
There really ae some numpties in the workshop!
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Deece55
L Plate Warrior



Joined: 21 Oct 2010
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PostPosted: 19:56 - 23 Oct 2010    Post subject: Reply with quote
carb is a mikuni vm19sc. standard bore 55.0mm, stroke 51.8mm. bore now 56.5 so surely new bore would be:
v=3.142 x 51.8 x (56.5/2)^2 = 129.87cc
p.s. yeah piston melted coz autolube failed when on long run, doing 65 on dual carriageway 110 miles into 200 mile trip. when get smell of welding u know not good! got towed bike 2 bike to next services then had to ride pillion n get bike recovered. still love her though!
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Deece55
L Plate Warrior



Joined: 21 Oct 2010
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PostPosted: 08:18 - 25 Oct 2010    Post subject: Reply with quote
Yeah she runs, started first couple of kicks. Doesnt want to run fully off choke though.
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hmmmnz
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PostPosted: 11:13 - 25 Oct 2010    Post subject: Reply with quote
logic says its running lean,
i own a couple a1 model kh125's and out of the box they are a touch on the lean side, any 2 stroke is better off running a bit rich than running at all lean, compounded with it being a air cooled engine,


according to my calculations you are now up to 131.4 cc up from 124.6cc roughly a 5%increase in capacity,
that is definite re-jetting territory
im not sure what main you are running, i'd say around the 95 mark, id go to about a 105 may be even bigger



Esoteric1 if your a mechanic, ill fucken eat my old boots,
you need to shut up, and do some research before you go and spout off and give out shit infomation
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