Poor mid to top end performance Scorpa 300 twenty

[gasgasshetland]

Hi there, just wondering if anyone might have any suggestions that I might try to resolve my issue. 
the bike is a 2015 Scorpa 300 twenty model. I bought it earlier this year and have had a few issues, so I will list what I have changed so far trying to sort the bike. It s running a keihin carb.

crank seals replaced, Reed valves and inlet block changed, new barrel and piston as it seized, new CDI, I also have set carb float height and tried a no3 slide, but it’s back on the standard 3.5 slide. It’s currently running a 128 main jet.

The bike runs fine at low revs, but if you try to open it up say in a hill climb or over the moor then it runs poorly and starts pinking. I have a 130 main jet that I am going to try, but if anyone has any other ideas what could be the problem that would be great as I’ve now spent so much trying to get this bike sorted out it’s doing my head in. 
maybe I should have tried the bigger main jet before posting here, but I will try it this week. Someone I ride with said had the new CDI been mapped to the bike, but I’ve never heard about that and don’t know if that is a requirement of  installing one.

Edited August 16, 2020 by gasgasshetland
Mistake in text

[topline620]

You might want to check the rubber inlet boot between the carb and reed valve,I presume they are the same as the Sherco which are a notoriously bad fit hence the weak mixture you are experiencing.

[misscrabstick]

Sometime, somewhere, I heard there was an issue with excessive compression ratio (pinking/detonation) and it was cured with a head insert, strongly suggest you contact Scorpa

[gasgasshetland]

Thanks for the reply. I will give them a call today. 

[gasgasshetland]

Inlet rubber was changed as the one on the bike had been bodged up

[nhuskys]

Don't forget the exhaust side, as it could be restricted. At your bikes age and with the fact that it was poorly cared for before you got it, I would remove clean the whole exhaust system and repack the silencer.

[gasgasshetland]

Thanks for reply. Exaust repacked.  I have spoken with Nigel Birkett today and he has given me some setting to do with the carb. Apparently these 2015 300s were problematic regards getting the carburation right. 

[dan williams]

What fuel are you running? With a high compression ratio octane rating is critical. You can jet richer to reduce preignition but then you are throwing away power. This can be especially bad if the ignition advance is aggressive. Beta's were notorious for this.

Edited August 18, 2020 by dan williams

[gasgasshetland]

We can only get 95ron fuel where I live. I’ve just tried some octane booster, but didn’t help. 

[dan williams]

That’s unfortunate. You may be best served by putting in a lower compression head. If it makes you feel any better I run the S3 low comp head in my Beta and aside from it not squirting out from under me as often it really hasn’t lost anything.

Edited August 18, 2020 by dan williams

[stpauls]

Check the timing mark.  I am wondering if the timing has been retarded to soften the power at higher revs - perhaps by too much.  About 3mm retarded (not degrees) will soften the power.  A bit more and it will run badly.    You will need to remove the flywheel to check this.  Special tool needed (E.bay, a few quid).