OzVMX Forum
Marque Remarks => Kawasaki => Topic started by: splime738 on May 23, 2014, 05:23:25 pm
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Just looking for some help with carb and jetting for my 250 A5, anyone running them what set ups are you using? I am in the UK, so it will be different to OZ or US but just interested to hear what is being run if different to stock with new fuel.
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Sure, I got two of them, they are fast & sorted...
MJ: 170 reverse type
Needle: 6F21 clip 3
Needle jet: R-0
PJ: 50
Air screw: 1.0 turns
In one carb I have fitted a different model needle jet so it runs a 370 hex jet.
I had a bit of trouble at the start as my carbs were the original on the bikes, they didn't run right until I replaced the needle jets, they had worn and were making it way rich at part throttle, lots of gunge dripping from the pipe joins.
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Thanks John,
my problem is I have seized a couple of times, been trying to use jetting from manual but it is obviously running too weak. When you say reverse main jet is that the round type with slot?
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If you are trying to tune a later model vm mikuni carby with hex main jet the the equivalent size to johns spec 170 is 370.
Cheeers Brett
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Thanks Brett, it seized at weekend with a 190 in it, I thought it was going to be quite rich.
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Thanks Brett, it seized at weekend with a 190 in it, I thought it was going to be quite rich.
If it seized with a 190 main its not lean, you've got another problem.
Mine runs a 175 main,
40 pilot
6FL28 needle in the 3rd position
R2 needle jet
It's well sorted and fast..
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That's pretty close to the original jetting there Jonny O, cheers, will have to re-check for air leaks again
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The std jetting is a 172.5 main and 50 pilot jet..
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Splime, What sort of seizure?
Did it get hot somewhere around the exhaust port, transfer some of the piston to the bore and also weld the rings to the piston?
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It didn't seize thru being too lean unless it has a bad air leak.
How's the piston to bore clearance?
Is the ignition timing advanced or compression ratio too high?
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It's well sorted and fast..
Anything is fast with you on it John :)
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Ignition is hopefully ok, it has just had a new old stock cdi, stator and coil fitted (silly money), marks lined up so it shouldn't be advanced or retarded, barrel height and head all standard with Kawasaki head and base gaskets. Barrel just been nicasiled and new piston. It has gone as oldyzman says around the exhaust port, went solid then freed off but has scrapped the piston and cylinder will need to be re plated.
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Forgot to say, running standard exhaust too with a Holly silencer
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Ignition is hopefully ok, it has just had a new old stock cdi, stator and coil fitted (silly money), marks lined up so it shouldn't be advanced or retarded, barrel height and head all standard with Kawasaki head and base gaskets. Barrel just been nicasiled and new piston. It has gone as oldyzman says around the exhaust port, went solid then freed off but has scrapped the piston and cylinder will need to be re plated.
you can try to remove any residual alloy with hydrochloric acid if the piston has left any alloy behind. The nicasil bores are pretty hardy :)
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id be sealing up the exhaust and intake ports and doing a pressure test on the crankcase to check for any air leaks. also id do what a lold timer told me and that is start off very rich and work down not start lean and sieze or cook everything as getting barrels replated aint cheap nor are new piston/rings.also check fuel flow from your tank and that the carb as the right sized needle and seat fitted
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Cheers for the info, will be checking crank case pressure when I get barrel back on, will pull it apart if any leaks on seals
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Make sure the piston to bore clearance is not to tight [maybe to hard now with the damage]......we just had a barrel re nickasiled 3 times because oldmate gave it to much clearance and the bore was tapered.....it took a little while to make the guy understand, hence we wont be using him again. Also are you using a genuine Kawi piston [NOS] or a modern one [Wiseco/Wossner].
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I usually like wossner, but in my A4 i had more luck with wiseco...
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piston to bore too tight and piston expansion will seize on exhaust port !
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I have been using Wossner pistons for a while now in all my other bikes with no problem. I have used this A5 for a while now, it never seems to pull right and then seizes within a couple of meetings, I bought all new old stock electrics in case it was the ignition gone a bit. I have even had an electrex world ignition (pvl copy) on it for a while. When the bike runs it feels flat, no bottom or midrange and almost like the clutch is slipping, which it isn't that's been changed anyway. Several people told me I need to go up on the jetting due to the newer fuel being poorer quality hence why I was asking about what jetting people are using. I have a new VM 38 on it set up with original spec jetting, until last week when I tried to richen it up still the same. Poor power then locks up and on inspection, front exhaust port damage. I have another barrel, but same results when that was on. I use a company called Langcourts for re plating and there work is good.
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Are you using a 190 round main jet?
What is the piston to cylinder clearance, has it been replated with not enough tolerance?
Has the head been machined for more compression?
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Yes a 190 round style main jet, piston clearance should be ok, the same company have done my 75 cylinders no problem, same bore size. No signs of machining on the head.
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There's obviously something not right, no use assuming everything is ok. You need to measure piston to bore clearance, compression ratio or compare cylinder heads and cylinders with other std ones in case head or top of cylinder has been machined, maybe try another ignition also.
Check for air leaks, replace the LH crank seal, do some plug chops to check jetting. Plenty of things to check..
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Problem will be the Wossner. QC has gone to shit recently
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Funny you should say that Lozza, i have a old wossner in my cr race bike for 2 seasons now, but in my kx had no luck with recent wossners...
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Whats even more odd is Wiseco seem to have got better. Had every type of fail with them as well, mysterious sinking domes, ring pegs pushed in to far, 'soft' alloy etc etc. Rings are very good on the other hand