nicketynoo Posted October 29, 2014 Share Posted October 29, 2014 Hi Have bought a RXS 100 and its really not running well. Firstly I'll give a bit of background about the bike. Its only done 3500 miles from new since 1989 and I believe this is correct due to previous MOT's and the condition of parts etc. When I got it someone had butchered the airbox and fitted a cone filter to it , so I fitted a standard airbox with a brand new original airfilter. The spark plug is a BR8HIX Iridium (not sure if this is the equivalent of a standard plug) The bike starts really easily and has plenty of compression and ticks over nicely but when running it feels as though its choked and won't rev out in any gear above 3rd. The max speed I achieved was 45 Mph which if I remember back to 1984 when I last rode one of these is pathetic. I checked the plug after a decent run and it was very wet which indicates too much fuel which concurs with the way the bike feels when riding it. I have stripped the barrel off and the piston top is quite black and there is a bit of burning past the rings at the exhaust port side which I think is normal,there is a small mark in the top of the piston again at the exhaust side , as though something small has hit it but really not much to affect running. A new piston kit is now on its way. The small end bearing is in perfect condition but this will be changed too. There is no play in the big end and bearings all feel fine. I have stripped and checked the carb and everything is standard (main jet,pilot jet , needle clip on no.2 etc) Not sure how to check the float height but looking at the line on the floats they werent quite horizontal so have set them so they are. This meant that the height was too small therefore more fuel in the bowl ( not sure if this would cause the problem). Also the only other difference from standard settings was the air screw was only 2 turns out instead of 2 1/4 . I have recently changed the crank seals as the gearbox oil reaked of fuel and pretty sure the seal on this side is fine, also I think if the seal on the flywheel side was passing this would let air into the cases and cause the opposite of what I've got. Any thoughts or pointers to look out for would be appreciated Thanks. Link to comment Share on other sites More sharing options...
blackhat250 Posted October 29, 2014 Share Posted October 29, 2014 Aye nickity" sounds like your on the case,,a fresh top end will improve her,, the air screw will help too, the float height is more important at W.O.Throttle, if its low it could lean out, Remember your probably heavier nowadays, so she"l be lucky to see 60mph oh and correct plug will help,,[ as book says,] Link to comment Share on other sites More sharing options...
nicketynoo Posted October 30, 2014 Author Share Posted October 30, 2014 Thanks Blackhat I'm definitely heavier but not enough to cause this, I can still get up to 60 on my sons aprilia RS 50 admittedly thats laid on the tank with me feet on the indicators, but somethings amiss. Hopefully new piston will be here today and then I can start tinkering. 1 Link to comment Share on other sites More sharing options...
YPVS TONE Posted October 30, 2014 Share Posted October 30, 2014 IF I remember rightly the RXS100 uses a foam type air filter. Did you apply oil to it when you put it in as you may have over oiled it as they should only be damp but not dripping with oil. The other thing to check is the exhaust baffle to make sure it's not coked up. I usually clean mine on the LC with a blow lamp to burn off the oil and carbon then use a wire brush to clean off the coke, making sure all the small holes at the end are clear. Can't remember on the RXS if the baffles came with any wadding on them when new but if yours has still got it on you can do away with it. Also you say it had a cone type filter on it when you got it and you've put the standard airbox on. Usually when you put a K&N type filter on you have to up the main jet to compensate for the extra airflow so now it maybe overjetted with the standard airbox on. Got a Yamaha data book that say's for the early 1983 RXS100 (31J) model it lists a #120 main jet as standard so maybe worth checking. Tony Link to comment Share on other sites More sharing options...
nicketynoo Posted October 30, 2014 Author Share Posted October 30, 2014 Thanks Tony Thats a very valid point about the airfilter I did squirt plenty of filter oil on it so that could well be a problem, I checked the main jet and it is #120 I don't think anything was done to suit the cone filter, thats the first thing I checked when I put it back to standard. I've just fitted the new piston and been out for a run and although it seems a bit better there's still something fundamentally wrong. It still wont pull in fourth and up. At least I can now see a dry plug and it is grey in colour, I would hope for a coffee cream colour if the mixture was correct. The wadding is still on the baffles and they are in perfectly clean condition as is everything else as its only done 3.5k there seems to be a knocking sound around 6 thousand revs , I have a suzuki rgv and it was similar to this and I raised the needles in the carbs a notch to lean it out and it made such a difference,may go and have another short run without the airfilter. thanks Nick Link to comment Share on other sites More sharing options...
YPVS TONE Posted October 30, 2014 Share Posted October 30, 2014 First thing I would do is get rid of the wadding on the baffle which is usually held on with wire wrapped around it and is not required. The Genuine air filter I got for my LC a while back came pre oiled so it may be an idea to squeeze out any excess oil from the one you have if you've applied oil to it. If you've fitted a new piston did you fit it with the arrow on the top of the piston facing forward towards the exhaust port ? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 30, 2014 Moderator Share Posted October 30, 2014 squeeze an over oiled foam filter between clean pages of newspaper it will soak up the excess Link to comment Share on other sites More sharing options...
nicketynoo Posted October 30, 2014 Author Share Posted October 30, 2014 Air filter is now drying on a radiator after a good wash out with fairy liquid. Have tried running with the needle in the carb down a notch and also with airfilter removed but still the same. I'm starting to fear the worse and suspect the knocking is possibly the big end! Have still got to try a new standard plug tomorrow as dont know if the iridium one is correct. If thats no better then I can see me stripping the engine down. Link to comment Share on other sites More sharing options...
blackhat250 Posted October 30, 2014 Share Posted October 30, 2014 Mind give the exhaust a clean out first as tone said , , main bearings are usually a rumble more than a knock,, Link to comment Share on other sites More sharing options...
nicketynoo Posted October 31, 2014 Author Share Posted October 31, 2014 And todays theory is?? Right just been for a new plug and some fresh 2 stroke oil. Whilst at the shop asked the mechanic to have a listen to her, and he says it sounds really choked up as though it can't breathe. Also had a look at the plug and this confirms its got too much oil. He suggested draining all the old 2 stroke oil off and fill with new since I didn't know what was in so have got a decent semi synthetic going in soon. I'm currently draining the tank now, whilst waiting I decided to remove the wadding from the baffle. I have also checked the setting on the oil pump and that is correct. Ok so whilst waiting I got impatient and started the bike with no 2 stroke going to the pump, I have run it now for a good 10 mins and it sounds like its breathing better and is still smoking. Therefore I have come to this conclusion:- The crank is full of oil/fuel from when the right hand side crank seal was knackered and so needs burning off or emptying somehow. It all makes perfect sense now and I'm really surprised none of you picked up on this . Come on the clue was in the first post So unsure of what action to take now don't really feel like stripping it back down at the moment so any thoughts Cheers Nick Link to comment Share on other sites More sharing options...
nicketynoo Posted October 31, 2014 Author Share Posted October 31, 2014 No more work required , have just been on a 20 mile blast and the bike is transformed, its running just as I remembered my old one did in 1984. It was great fun to ride and took me back 30 years. Thanks for your suggestions and support guys I'm one happy man! 1 Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 31, 2014 Moderator Share Posted October 31, 2014 Great news, yeahyou hit the nail on the head with that residual oil in the crankcase Link to comment Share on other sites More sharing options...
Recommended Posts