hey guys i hope someone can help me out
i have a nsr250rk5 mc18 which is sick as a dog

it misfires when running
overheats very quick
throttle rsponse is crap

have cleaned carb, filter, new plugs
did notice the cable for the oil pump was lose so i changed it to the settings you have on the tech page
but still runs the same

the bike is total standard
im a amatuer when it comes to fixing things so i hope someone has any advice or help

Sounds like ignition system/PGM or check the charge system first. Bad rectifier will cause that.

What colour were the old plugs?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

so gonna have to take flywheel off to do the ignition system then move plate left or right is there a way of doing or just guessing

my bike is at work so i check rectifier and battery tonight
not sure what voltage it should be reading though

plugs were jet black when i took them out not oily

thanx for the replys guys just wondering why it's overheating so much aswell

For trouble-shooting the regulator, the Electrex guide is very helpful (http://www.electrexusa.com/electrex_fault_finding.html) - tells what the voltages should be at idle and at various RPMs.

Re heat probelm, start simplest and work up - check coolant level is okay, then check thermostat, etc. - I had the impeller (sp?) shatter once - bike would overheat real fast!

Good luck.
-Jim
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-Jim
'93 MC21

big thanx guys for the info much appreciated
well ive just ordered a new reg/rectifier just incase

just wondering is there a way of telling that the ignition system is spot on or you just tell by the ears
i just wanna make sure i don't make a mess of it
also could it cause damage to the engine if the ignition system ain't set correctly

ok got my bike home last night been trying to get this damm nut off the flywheel this suker aint gonna budge gonna keep spraying with penetrating spray
is the nut anticlockwise to undo
wanna make sure i aint tightening up instead
more worried about the flywheel coming now cos of the seized nut
can anyone in the uk recommend a shop for the flywheel puller please

Stop , why are you trying to pull the flywheel off? dont dig yourself a deeper hole,I think you might need someone with a bit more spannering knowledge to help you out , its not neccesary to take off the flywheel

yes, I agree, why start with the flywheel? Have you already verified that the charging system is working properly? I think it better to rule out simple (and inexpensive) possible causes first.
-Jim
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-Jim
'93 MC21

? wrote:Stop , why are you trying to pull the flywheel off? dont dig yourself a deeper hole,I think you might need someone with a bit more spannering knowledge to help you out , its not neccesary to take off the flywheel

deeper hole more like my coffin
damm seems i'm making a mess of things allready

thanx guys looks like i'm gonna need step by step here

charging system gonna check tommorow got work soon

its not neccesary to take off the flywheel ??????????

no need to remove flywheel to determine condition of battery and regulator - just a volt meter and access to the battery needed.
-Jim
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-Jim
'93 MC21

Where in the UK are you? Sounds like one of us should drop by if possible!
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Dave Ett wrote:Where in the UK are you? Sounds like one of us should drop by if possible!

might be a good idea but i'm in manchester
sorry to be a pain in the arse guys i just aint a smart arse when it comes to bikes

got myself another set of carbs on the bike now
still got my prob but aint as bad
checked battery getting 13v
reg/rec not sure what readings i should be getting but gonna order a new one as a spare
but not to sure if this is the one its for a Honda NSR 250 RSP (R4J) R (RSK/RSK-11)RSP(R6K/R6K-11)(MC18) (import)

Code: < >

http://shop.wemoto.com/pictures/hl/aeb10.jpg

but has only 6 wires and looks alot bigger

Go here and follow this chart. this will help you check your charge system.

http://www.electrexusa.com/electrex_fault_finding.html

plugs were jet black when i took them out not oily

This would indicate a mixture that is WAY too rich.


got myself another set of carbs on the bike now
still got my prob but aint as bad
checked battery getting 13v

OK, first, if the Reg/Rec is on the way out, you would almost certainly see "spikes" in the reading on the voltmeter when you tested the battery, especially as you wind the throttle on to bring the revs up. You should have a fairly constant reading as the revs rise and fall of around 13.5 - 14.5V.

As Jim says, double check the coolant, making sure you have no air-locks that would cause a false indication of coolant level. Ideally you should check the thermostat operation.

First thing I would suggest is a compression check.

You say that fitting a new set of carbs has partly cured your problem. Well, this would indicate a settings problem. You say you've already fitted new plugs, cleaned the air filter, and adjusted the oil pump, which apart from the possibility of dud plugs (not impossible, but highly unlikely!) would mean you're following good procedure and under most circumstances, would've cured your problem! Check the plug gap, to be sure, which should be 0.7 - 0.8mm.

Check the carb settings. On the side of the carbs there is a "type" number. For the MC18Rk you should see TA21A.

The main jet size should be #128 for both carbs.

The PJ should be #75 for both carbs.

No.1 carb (top cylinder) should have the needle BPG, the No.2 carb needle should be BPH.

Slow jets should be #38.

The Air screws should each be set to 2 1/8 turns out from closed.

While the carbs are off, remove the intake manifold. Check the rubber "boots" for perishing or cracks that could be causing an air leak. Check the reeds to make sure there are no broken petals. Use a gasket each side of the reed valve blocks as the sealing ability of the rubber face of the inlet manifold deteriorates over time.

How does the bike idle? If it idles cleanly (or even just runs OK for testing purposes!) then that is a bonus! Start the bike up, and while running, spray carb cleaner around the intake manifold. If you have a good tight seal between the carbs and the airbox, and the gaskets on the manifold are doing their job, this will nicely clean the crankcase! If however, the revs rise, it would indicate you are drawing air, and this MUST be sorted before you go looking any further.

Spray carb cleaner around the back of the flywheel too. Same rule applies: if the revs rise, the crankcase is drawing air - not good, and pointless chasing around for other faults.

If the carbs settings seem OK, there are no apparent leaks, and there is a good constant reading across the battery with the engine running, check the coils. Is the misfire noticeable on just one cylinder? If so, swap the coils. If swapping the coils, the misfire swaps cylinders, then a new coil is the order of the day! (Normally I'd probably try this first, but as you say fitting another set of carbs has partly cured your problem, their settings need to be done first!)

If the misfire continues, it would then indicate either a bad PGM (ignition control unit) or possibly even a compression failure due to worn or broken piston/rings.

Can you let us know how you get on, and what symptoms you are still encountering after following these steps, and we'll see what else you can do.

Andy.
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