Mysterious problem with Gilera rcr 50. Please help!

[jasper090]

Hi,
I've got a Gilera Rcr 50 as mentioned in the title and it's playing up big time! It all started once I had run it in (I seized + melted the piston... twice - I just underestimated the importance of 500+ miles to run it in) so I started opening up the throttle more than usual, I hasten to add, I was not ragging it! but doing down hill 45/50 mph the bike would suddenly loose all engine power and cut out - but carry on running because the engine was constantly being turned over i.e. bump starting. Once the bike slowed down to 5 mph the bike would come back to life.
This happened rarely but only down hill. Then it started to happen on the flat, and now up hill.
Initially I thought it was fuel starvation so I checked and blew out all the fuel pips, the carb, filters, you name it I cleaned it... 3 times over cause it continued to cut out.
I have checked all the electrics to make sure there isnt anything earthing out and I have checked its nothing to do with the throttle cable. The bike is currently with the mechanic where it is continuing to baffle the mechanic, he has no idea what it is either.

I would be extremely grateful to anyone who has any idea what it could be as its got to the point where I am getting really quite frustrated with its mystery!

Jasper Mowatt

[InspectaBike]

[jasper090]

It was originally running rich, but the mechanic rectified that so its running just about right now.

[Ariel Badger]

[InspectaBike]

Does it do this when cold?

Another back to basics have you checked Plug & Lead are not breaking down when the bike warms up
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www.inspectabike.co.uk

[InspectaBike]

[jasper090]

haha, it was already cocked up before i took it to him . I hate taking the bike to him (he did the pistons as i figured it was best he did otherwise i would have screwed thing up further) cause i always come away with a nice large bill!!

in response to Inspectabike, originally it didnt do it whilst cold, but now it does it if you go faster than 30 for more than 10 seconds!!

[InspectaBike]

[jasper090]

Hopefully not otherwise it could be awkward when i next see him! Yeah the bike ticks over fine; no fault there...

[jasper090]

...

[jasper090]

Some one said it could be a problem with the cdi, does this sound like a possible cause?

[Usher4566]

Yes its possible and possibly expensive .45/50 is ragging it its a50 yea
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New cd200 benly owner

[jasper090]

[karthead]

[Usher4566]

Come on 45/50 has got to be more than recommended to run in a 50 .what's top speed .I had an ar50 when young and had every performance part it could have touched about 69 but you had to rag it .I would say 30 would not be raging it
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New cd200 benly owner

[jasper090]

[Usher4566]

O rite my mistake sorry mate .dad brought me a cg 125 wen was younger brand new said you gta run in .of course I ignored him .but never went wrong lol
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New cd200 benly owner

[jasper090]

[HD]

Back to the fuel starvation issue, have you tried replacing the fuel tap? They are vacuum so it may be knackered inside and the vacuum circuit may not be working. Check its connected to the carb as well.

Also, how sure are you the mixture is good? Have you checked the colour of the spark plug?
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Rusty '02 Vito Camper + CBR600F3

[nathan k]

[jasper090]

[jasper090]

Oh and also, I am fairly confident the mixtures good. Tomorrow i shall have another look and see what i think and make any changes if necessary.

[skatefreak]

blowing up an engine through not running it in properly?
Sounds a little fishy to me....
The wear in period is just to allow the rings and components to seat and bed well before putting it under high load.

I would be extremely suprised if you melted a piston by ragging it in the break in period. Sounds like there was a problem there from the beginning and its been melting your piston.

One cheap/easy way of ruling out the mixture (one of the more likely things issues to play a part in melting a piston) is to get a fresh, new plug, throw it in and after a few miles riding about pull it out and compare it to a chart like this:

https://1.bp.blogspot.com/_Zl3HQgWfsPc/TAaRbYTjUnI/AAAAAAAAD9M/mMWXiGIFQMY/s1600/honda-spark-plug-inspection-chart.jpg

Have a stab at it, extremely basic and you can upload a picture of the plug. Will tell you lots about how the engine is running


Also two stroke i'm assuming?
What oil are you using? Is it premix or does the engine have an oil pump?

Best regards

-Jvr

[jasper090]

Steakfreak,

I shall get a new plug tomorrow along with replacing the cdi. if i can actually ride it for two miles i shall post a picutre of the results however it is in a car park broken down at the minute . Problem seems to have deteriorated. tt is oil pumped and yes it is two stroke. Hmm, i can not remember the name of the oil but its synthetic and its red.... I got it from the bike mechanics so i just assume its a good one. thank you

[jasper090]

Update
Well it started working just fine... I replaced the CDI and blew out the carb again and the problem momentarily stopped untill this after noon when i was going up hill and it bogged down - but in first gear it still would pull me up, it seemed if i went faster than 10 mph it would bog down... So i rode for about 5 miles at 10mph untill i decided to try and see whhat it worked like at higher speeds, gear two, 3, 4 and 5 would all bogg down but if i went to 6 and full throttle (so it was being ragged) it would work fine with absolutely no loss of power.
Is this a new problem or is it the original just re-occurring slightly differently?
Any ideas??

Oh and the spark plug looks like picutre 10...