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Discussion in 'Your 250cc Projects' started by Linkin, Apr 3, 2019.
Mine's running actually
Doing a bit more after work... got an exhaust pipe that was meant for the ZXR but never made it on.
Cut the stock pipe off and weld the new flange to the link pipe. Problem is, the outer skin of the link pipe is stainless, with a smaller steel pipe inside, which is very thin. Rather than weld from the outside, I will try from the inside first.
The stainless will weld fine to the mild steel, you just need to paint the welded area so it won't rust.
Finished off the welding on the exhaust pipe today - the inner mild steel section was broken inside so the pipe was loose in the stainless outer... welded the stainless to the adapter plate supplied with the pipe and now it doesn't leak. Probably need a new gasket for the link pipe but not going to bother... I had other running issues to find.
Went in and balanced the carbs, found a dodgy repair on #4 vacuum plug, so it was leaking. Replaced with a spare from work... as for the balance... I'll let the picture do the talking
Have to do some fine tuning of the mixture screws again (too hard when the bike is hot). At least now I know the radiator fan works, I'd never heard it run and saw it running - it is actually working, just quiet.
Still waiting on the rear shock... like riding a pogo stick!
Rear shock arrived and fitted. Pulled apart the knuckle and serviced it. Bearings ok except for one which was a bit dry and stuck. Managed to free it up and get it full of grease, it kept jamming... I had to keep cleaning, regreasing and rotating it until it finally freed up enough to be serviceable. It was that or leave the bike and catch the bus home.
Shock arrived pre-configured and after a ride home I don't think it needs any adjustment for solo riding. For 2-up I will need to add some preload adjusters or something to the forks. Sag feels nice and even.
what are the details of the rear shock?
I'll be after one for my son's GSF250 in the not to distant future..
Provided that is, that the replacement engine we bought works out ok once we get it installed.
I bought it from wemoto.com.au
No wrecker in Sydney had a standard seat. Found one on buyee for $50 so I bought it. Naturally postage from Japan was outrageously expensive at $115, but it's worth it to not have a sore bum all the time. And it's still cheaper than a new OEM seat.
New seat arrived yesterday. Put in and took it for a ride. Immediately binned the old one. What a difference! Can't believe I put up with that thing for so long.
Last friday I started on the carbs.
Jet housing arrangement - non removable
Pilot merge chamber
I discovered a problem with my replacement float bowl, the extended portion that protrudes into the merge chamber is different to the other 3 original. I am not sure what effect this would have, but I don't like it. Suzuki don't list the float bowl as a standalone part, only a whole carb assembly.
The BST29SS carbs also have slide housing seals like the fizzers
The pilot jets had been butchered, I managed to get three out but the last one rounded off. I had to use a snap on screw extractor set (a quality bit of kit) to drill into and extract the jet. Worked like a charm.
I need to pick the brains of those experienced in re-jetting bikes. With the aftermarket exhaust, there is a hiccup right at 14,000rpm at full throttle. I suspect a lean condition due to increased flow of aftermarket exhaust.
A problem the bike has always had is boggyness on the pilot circuit, up to about 4,000rpm, regardless of mixture screw setting.
The main jets are 97.5 and pilot jets are all 30 (non bleed).
My boss suggested that going down one pilot jet size and up one main jet size would be a good starting point, then adjusting via mixture screws and needle settings later.
Trying to get away without dyno tuning it as I'm paying for the R6 to get done
With the hiccup at 14,000rpm, does it feel flat and just not rev anymore ? If so then i would go up 1 size on the main jet
If it was too rich it would be boggy at high rpm's and slowly die off
With it being boggy at 4000rpm you could try dropping the float height .5mm to 1mm , you would need to adjust the mixture's again once it's warm as you'd know
Okay, clarification. At around 14,000rpm in 3rd gear at full throttle, the rpm stops increasing and it feels like misfires. It occurs once and the next time is OK. My gut feeling is lean condition but I'm no expert.
From idle to around 4,000rpm the throttle response is slow, it feels boggy and slow to rev no matter the throttle position. My gut feeling is it is rich - backed by excessive fuel usage. Needles and emulsion tubes are all fine.
MikuniOz don't have any pilot jets below size #30. I plan to replace them as they're all butchered, have reset mixture screws to standard (1.5 turns) and re-balance/tune the bike.
Midrange all feels okay.
Show and Go here in SA would most likely have the Pilot jet's
I have had stuttering from too rich jet's before
2 cents worth: I always go down in main jet until it has that hesitation/misfire at peak rpm (sounds like yours) then I go back up one size. As for the pilots, just source some smaller ones and give them a try.
I'll be interested to see your results/settings on this one. My GSF250V has the full Yoshimura 4 into 1 system on it. Not sure if the jets etc are the standard ones or not. But at least she is all up and running now with the replacement engine.
Ok, so I finally dug into the top of the mighty bandit motor
Took me a while to get my head around the whole arrangement, but I have a handle on it.
Adjusted all the exhaust tappets, all a little tight but above minimum - screw and locknut arrangement, no shims. Easy.
Inlet side is where the headache comes... stay with me now...
My low speed clearances are above minimum at around 0.13-0.15mm all around. Hi speed clearances are a bit tighter but still OK.
The rocker arm play was a headache but I got them all set at 0.20mm. The system sounds ok switching TO high speed rockers, but when decelarting and shifting down to low speed, I must have something out spec as it sounds like it's not engaging straight away, with a rattly noise.
I did not change any shims as I didn't have the special ones needed from Suzuki, and I had to put the bike back together to get home.
LO speed clearance - shims between low speed rocker arm and valve spring retainer. Rocker arm shaft fully counter-clockwise. Camshaft mark (right hand side of engine) must be at 6 o clock for cylinders 1 & 2, and mark at 12 o clock for 3 & 4. Clearance 0.10-0.20mm. Shims are changed by sliding the rocker arm out of the way with a set of needle nose pliers, you can do four shims at a time. No need to remove camshaft.
HI speed clearance - shims located between low speed arm and high speed arm. Rocker arm shaft must be rotated fully clockwise to engage hi speed arms. Measure clearance between main rocker arm and hi speed rocker arm. Clearance 0.10-0.20mm. Shims are changed with the rocker arm shaft rotated fully clockwise and again just sliding it out of the way with needle nose pliers. These are the special shims with a pin underneath to seat them in the main rocker arm and would have to be ordered from Suzuki.
Sub rocker arm play inspection
Rocker arm shaft rotated fully counter clockwise. Check clearance between main rocker arm (low speed) and sub rocker arm (high speed). Clearance 0.10-0.25mm. If there is difficulty inserting the feeler gauges, rotate rocker shaft clockwise by 30-60 degrees.
Sub rocker arm adjustment
Rocker arm shaft must be rotated fully counter-clockwise. Measure clearance between hi and lo speed rocker arms. The manual states "Turn the crankshaft until the intake cam nose of #2 cylinder points the direction perpendicular to the cylinder head mating surface"
Translation: If you can't get at the screw and locknut adjusters, rotate the engine until the cam lobes are out of the way and the rocker arms are free.
Additionally: All inlet clearances on the same cylinder must be within 0.05mm. Unsure if this includes the rocker arm play.
Video of rocker arm engagement, excuse the poor quality and no audio, my iphone decided to select the wrong mode and sped up about a minute of video into 7 seconds, I had to stretch it back it in a video editor.
Remind me to never own anything with 'variable cam timing'. So did it fix the other problem you were having?
Seems to have fixed the misfiring I was experiencing