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Discussion in 'Your 250cc Projects' started by Jethalter, Mar 27, 2019.
Hahaha. You go girlfriend.
I have a theory about these 250's. A lot of them are grey imports and when they were new, their good little Japanese owners rode them to the corner store and never exceeded 5000 rpm. Otherwise they would have go to the police station and surrender themselves out of shame. The other thing I noticed is that when I honed my 400 bores the sleeves were damn hard. That means you have to flog the ring piece out of it from the get go if you want the rings to seal and have any compression at all. Everytime I hear a tale of 'My Suzuki Bandit Has no Compression' this is what springs to mind.
I'm not quite sure how you making me feel there.
I'm partial to giving it hell, but realistically not to the point your bouncing off the rev limiter.
I usually vary the rpm a minor amount from cold, not letting it idle, once warm i take it for a moderate fang for a few laps, all things good then i give it hell for a bit. Then after that initial run, i ride spiritedly and vary the rpm a bit.
If i'm running in new camshafts, its a bit different process, but that only takes 20 mins. and after that the above applies.
Pistons, Cylinder Barrels, Cylinder Head all been soda blasted today.
Pistons also been ultrasonically cleaned and the barrels and head have been diesel cleaned + air.
Camshaft caps have been ultrasonically cleaned also.
Valves will be cleaned and then dye marked to check against seats, however i think most should seat pretty well and the seats cleaned up really well on the head.
The amount of dirt/crud that was cleaned off the surfaces of the barrels and head was phenomenal compared to how it looked 'pretty clean' beforehand.
If i get the chance i will post pics, still waiting on valve stems and piston rings tho :-(
So in preparation for finally getting this motor back together (still waiting on rings and stem seals )
tonight i cleaned all the valves and dye marked the seats and checked how well they sealed.
Every single valve seals identically and quite good. No lapping needed
So i'm thinking part seal problem i had previously on the leak down was due to possible carbon build up.
Anyway another step closer to being done.
Anyway here is some pics, The barrels and head cleaned after soda blasting and soaking.
Here is the valves after cleaning, you can see some comparisons.
Here is the valves stems being dye marked and checked for need of lapping.
Setback, the valve stem seals i got were the wrong ones. So i had to order a set of genuine seals from overseas at half the price of the Suzuki Australia price. Could take a few weeks to arrive :-(
On a positive note, My piston rings arrive from AHL today.
Here's is a comparison for sizing.
AHL - Thickness
1st Ring Comp - 0.78mm
2nd Ring Comp - 0.78mm
1st Oil Ring - 0.40mm
Wave Oil Ring - 1.79mm
2nd Oil Ring - 0.40mm
OEM Used - Thickness
1st Ring Comp - 0.76mm
2nd Ring Comp - 0.77mm
1st Oil Ring - 0.34mm
Wave Oil Ring - 1.75mm
2nd Oil Ring - 0.34mm
So overall none of the Chinese AHL piston rings are undersized.
The little bit larger thickness on the oil rings is no issue with fitment.
One could determine that possible wear on the oem rings is perhaps why the oil side seems a little undersized.
Either way least one worked out well for me so far. Next step is honing the cylinders and fitting the pistons and barrels back together, then waiting for the genuine valve stem seals to arrive.
Valve Stem Seals came in today The correct genuine ones too.
So in the next couple of days i should have the engine all back together.
Just for peace of mind whilst im in the midst of it all, i got some super fine lapping paste im just gonna give the valves a touch up, they dye marked fine, but if there is any small rough bits i just wanna get them out.
Hopefully by the weekend i have a running across again :-D
Even tho the weather is shite.....
Cylinders honed, pistons fitted, cylinders fitted.
Valves finely lapped to clean surfaces, Head assembled, Fitted, Cams and timing in place.
Next to go is valve clearances, everything is just a smidge on the tight side i suspect, will have to see what i can muster shim wise from my other motors.
Engine all done, and fitted in the across. Still gotta bolt everything up and connect wiring, run it, make sure everything is good, put fairings on etc...
Valve clearances as follows :
Exhaust, Valve, Reading
1 - 1 : .203
1 - 2 : .203
2 - 1 : .229
2 - 2 : .229
3 - 1 : .203
3 - 2 : .229
4 - 1 : .229
4 - 2 : .229
Inlet, Valve, Reading
1 - 1 : .203
1 - 2 : .203
2 - 1 : .203
2 - 2 : .203
3 - 1 : .229
3 - 2 : .203
4 - 1 : .203
4 - 2 : .203
The Manual says Inlet is .17 - .25 and Exhaust is .20 - .30
The inlets are all spot on, The exhaust side 1-1,1-2,3-1 are a touch on the tight side but still within spec.
I could have gone through all my motors and such to get it a touch better, but i dont want pieces of motors hanging about and since its all still in spec, it should be fine.
I'll be rechecking them at 5000 kms and see from there.
So filled it up with fluids, fitted carbs and air box , everything minus fairings.
Tried to start it, nothing, wouldn't start. checked fuel, had heaps, checked spark had spark. 100% i set the timing right cause i triple checked it and was spot on to the manual indications.
Redid the leads to a wasted spark 4 cylinder order, left coil 1-4, right coil 2-3. Bam fired right up.
Blew tons of white smoke for about 15 mins, varied the rpm during this.
At the end once it was hot, no smoke.
At a guess this is how long it took to burn off the oil and bed the oil rings in to seal.
So now letting it cool down, will fit fairings and go for a ride tomorrow or so.
Must say it sounds much more tough in its revving. Fingers crossed good things.
Still got the hard start issue, thinking its a combination of too large pilot jets causing rich starts (no choke needed, ever. my old across i had many years ago, put choke on, push button and starts easy as).
Also going to look at possible replacement coils, whilst there is spark and was checked, i'm leaning to it being a touch on the weak side perhaps.
Tho today's test ride was fun, she saw 17k rpm quite a few times. Compared to before it sounds super smooth in the rpm range and the exhaust also sounds way smoother.
Gonna be a bit of testing over time i think still, least i can rule out the engine as the problem. Can't comp test till rings are full bedded in and 30km's so far wont have done that.
So after the ride today which was fun, i've let it cool completely and started it again.
It did manage to start quite quickly, but its doing its old tricks. The first 5-10 seconds it runs rough, sounds almost like its misfiring, maybe richness ??? but after that, comes good and rev's very spiritedly.
I'm wondering if its possibly the coils ?? Anyone like to chime in ??
Sound more like too high float levels. Have you checked them?
I haven't checked them since the carbs were rebuilt.
When they were, new float needle and seats were used and set accordingly.
I put new needles into my CBR MC-14 carbs and last Sunday had to reset the float level as they had settled in and raised the fuel level 3mm.
Will check it out tomorrow and let you know how it goes
Checked the float levels, 20.50mm as manual stated, manual said -/+ 1mm, so i set them at 21.50
Issue is still apparent. when cold very hard to start.
I had to turn the idle screw off to 0, to get it to pop and fire
Main needles set 2nd down from top.
When it does finally start cold, it runs for about 5-10 secs like ****, kinda like a rough fuel/miss. After that, it rev's up quite happily and idles fine.
When warm and riding, its rides very well, no apparent loss of any power etc..
Also, the more i think about it, i thought perhaps carbs, but this set of carbs on the bike now is the set that have been fully rebuilt, and the old set that was cleaned up gives the same result.
Not too sure where to go from here to be honest. I thought possibly coil packs, but once its warm and running well, it revs to 17k rpm no problem. That generally would rule out any coil issues.
Spark plugs are also less than 500kms old.
Have you checked the resistance through the spark plug caps ?
And have you adjusted the mixture screw's to get the highest/smoothest idle speed once the bike is warmed up after a ride
I haven't but all i can think about at the moment is its less related to spark and something more with carb issue.
The reason i say is the fact it only effects starting. If it was coils/spark issues, the problem should be apparent at high rpm.
I went to the bike this morning and a tiny 50c puddle of fuel from where the overflow tubes are. So im thinking that one of my float needles isnt seating right / faulty. The result is as the bike sits more its possible its draining fuel into the cylinder and the longer it sits, the more fuel in there and the harder to start. Where as if you turn it off, then press start, it fires straight away and idles straight away no throttle needed.
I've got some spare float needles and seats that i can try that are new (when i ordered i got 4 instead of 2).
They are the Keyster - KYV33020
So this is where im going to look at the moment. Every other scenario i think of, just doesn't make sense to me.