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Classic Bike Trackdays

1983 RG 250 Gamma Accelleration issues

 
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Lollie



Joined: 30 Mar 2016
Posts: 15
Location: Adelaide South Australia

PostPosted: Tue Apr 05, 2016 5:45 am    Post subject: 1983 RG 250 Gamma Accelleration issues Reply with quote

Hello everyone, I have finally purchased a hobby/toy and after doing all the basics necessary for a machine that has been sitting around for 13 years she runs. There is only 30,000 Km on the clock, one owner before me and I have the original service manual etc. My location is Adelaide South Australia.
The issue is - when full throttle is applied, the engine bogs down as if there is only one cylinder working. When ridden at up to say 3/4 throttle, the thing sings sweetly well past the power band and through redline. I am using 50:1 premix to avoid any mixture issues from an incorrectly set oil pump. The carbies are all clean, new pilot jets, standard main and needles, float set to spec, ALL electric pick up coils are fine and the engine coil reads (DC at least) what the manual says it should be. New spark plugs of course, replaced all the fuel lines, cleaned out the tank, cleaned out the exhaust pipes and mufflers. Starts OK but for the first 10 seconds or so the left pot seems not to be firing (evidenced by the lack of exhaust from it). When the choke is applied during the problem it gets worse. Take out the air cleaner and remove the airbox cover and the problem up top is not as bad, but I think the revs down lower are not as nippy.
Leads me to think there is a "Too rich" problem??? Has anyone out there seen this before? If so I would really like to hear how you overcame the issue. It means that I can never extract full power from the otherwise lovely machine!
Thank you all in advance for your consideration. I hope there is enough basic info to work with.
Lollie
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StrokerBoy
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Joined: 15 Nov 2006
Posts: 1238
Location: Oop North, UK

PostPosted: Wed Apr 06, 2016 10:26 am    Post subject: Reply with quote

Hi, and welcome.

It does sound like it might be too rich. Can you get it to full throttle eventually if you open it gently ? Have you synced the carb slides and checked the cables - they might be opening at different rates if a cable has stretched or is badly routed ? Is the airfilter new/clean ?

Despite all your work ensuring it's in stock spec, it is a 33-year-old bike, so various bits will have worn slightly. So you might need to vary the needles etc from stock to optimise it now. Make small changes and do them one at a time.

I'd be looking to confirm the oil-pump is working fine and then forgetting the premix to be honest. I assume it's not getting pumped 2T oil as well as the stuff in the tank ?

Sounds like there's not much wrong with it, good luck ! Very Happy
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Straycat



Joined: 22 Jul 2015
Posts: 165
Location: Canada

PostPosted: Wed Apr 06, 2016 11:38 am    Post subject: Reply with quote

May want to do a plug chop and check to see the colour of your plugs too.

if she's good upto 3/4 throttle and bogging after that tells me its having trouble when your main jets take over (its the mains that control the fuel flow from 3/4 to full throttle)

id pull your carbs again and check your mains. Did your new mains have a number stamped on them or were they unmarked in a rebuild kit ?

I got a rebuild kit for my RG250, the pilots were stamped and the mains were not. I refused to put in the unmarked mains, I want to know exactly whats going in so im not chasing ghosts if its running lean or rich when i finally start running it.

Just an idea
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2014 Honda VFR800
2015 Yamaha FJ09
2000 Kawasaki ZRX1100
1989 Yamaha RZ350 ypvs
1989 Yamaha FZR400
1987 Suzuki RG250 Gamma
1986 Honda NS400R
1988 RGV250 VJ21A-J
1986 Honda TLR200 Reflex
1985 Honda VF1000R (x2)
1985 Yamaha RZ500
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Lollie



Joined: 30 Mar 2016
Posts: 15
Location: Adelaide South Australia

PostPosted: Wed Apr 06, 2016 11:57 am    Post subject: Reply with quote

Thanks StrokerBoy.
I found out from the previous owner that at the time he stopped riding the bike it was running with way too much two stroke oil (evidenced by the huge amount of oily crap and sludge that fired out when it started and got cleaned out later with my copious kerosene and water washes - the cans are sealed and I don't really want to cut them apart).
I don't have an accurate way to check the administration of the oil so to save the trouble for now until the bike is running well I simply emptied the pump of the two stroke oil and am running it premixed from the tank. I will more than likely restore the oil injection once I am happy with the way it goes.
As far as the syncing the slides, I haven't done it specifically but not having played that much with carburettors they looked quite in sync to me - as a novice - when I put them back on after cleaning them. Do you know a procedure to get them really accurate or simply from zero to maximum at the same time?
The air filter is new.
At any stage full throttle will ALWAYS cause the engine to run really badly, even when applied slowly/gently.
Another point which may indicate something to someone in the know is that I cannot make the bike go past about 110 Kph as the same problem occurs at any throttle position in any gear. If I get below the bubble I get a fraction more from it but it could be con strewed as though the electrics are breaking down under load? I wish I knew more. Perhaps you or someone out there can help?
In the meantime, I will when I get back on to it in the next few days start changing the needle positions and should I perhaps get some smaller main jets too to try do you think?
Thanks again everyone.
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Lollie



Joined: 30 Mar 2016
Posts: 15
Location: Adelaide South Australia

PostPosted: Wed Apr 06, 2016 12:05 pm    Post subject: Reply with quote

Thanks Straycat,
No I didn't change the main jets. The primary jets were totally clogged and were replaced with the correct same value, but the mains seemed to unblock OK. I did however push a very small wire through them to ensure they were all totally unblocked. Could I have damaged them and inadvertently enlarged one or both of them do you think?
Thanks for your input folks.
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Lollie



Joined: 30 Mar 2016
Posts: 15
Location: Adelaide South Australia

PostPosted: Thu Apr 07, 2016 8:11 am    Post subject: Reply with quote

Well then, another lot of info.
Following you good folk's input, today I once again removed the carbies (which I am sure you all know isn't just a 5 minute job on these things) and had a really good inspection of a: carbie slide sync, and b: main jets.
Both obviously required attention. The slides were around 1 -1.5 mm out of sync from each other and there was a major difference in the size of the two main jets... who knows why!
The numbers were either worn off, not there or corroded from the jets so I went and purchased some stock 165's as per manual from a local Go carting specialist.
The new jets are about as big as the one with the largest opening from the two I removed today and consequently noticeably larger than the one with the smaller opening.
After installing these and trying my best to get the slides in sync, I reinstalled everything and went for a ride.
Apart from it not idling (which I fixed later when the engine was warmer) it appears that the "bogging down" has vanished! I am really happy! Thanks guys, you stimulated me to action in the right direction.
Now... as far as the overall performance is concerned, not knowing this model - I have only ever owned and still own several four strokes - I feel as if it could go much better at the very top end from 8500 rpm through to redline.
QUESTION: What sort of power delivery characteristics did these things have new, and can some slightly larger main jets help a little up at these higher revs?
Thanks again.
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Lollie



Joined: 30 Mar 2016
Posts: 15
Location: Adelaide South Australia

PostPosted: Thu Apr 07, 2016 11:06 am    Post subject: Reply with quote

Just one clarification, I just went for a decent ride then and I feel that the power is down from around 8000 rpm up... NOT 8500. I was thinking, how does one adjust the timing on these machines? The key on the rotor doesn't give one many options hey?
Thanks again in advance. Wink
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