350B race bike - more power needed - MVAgusta.net
LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 05-16-2016, 11:53 AM Thread Starter
New Member
Join Date: Jan 2014
Location: Derby, England
Posts: 23
350B race bike - more power needed

Well after taking the MV out on a number of PR6 parades in 2014, I decided to race her at some of the CRMC and VMCC/BHR events and we had a lovely time at Cadwell, Mallory, Darley Moor, Donington and Snetterton. We were never in contention with the highly tuned 250 and 350 Ducatis, and the B.E.A.R.S. series was very serious at the 500, 750 and unlimited level, however I managed to set the lap record at Mallory Park in the F1 category!! We were out on the Lap of Honour at last years Classic TT but were very pedestrian on the fast sections.

The reason I'm telling this tale is because she's not been running well. At full throttle in top gear she bogs down or slips the clutch. Over the winter I pulled the clutch apart, cleaned up all the plates, disassembled and rebuilt the carbs, and ran her again - the slipping clutch was worse. I had the plates properly re-lined and new discs ordered from the ever helpful MV owners club spares department, but the clutch plates were full thickness and I couldn't get all five plates into the basket so I ran her with only four. However this still meant that I couldn't get the reaction plate in the right place as the springs were almost completely compressed. So I ran her round one of the local sprint courses making clutch-less gear changes but she was still not happy.

So I took her to the local dyno shop (Melted Sliders near Burton). The clutch kept slipping but we got enough of a run to find out that she is running REALLY rich. I've got 105 main jets in and have the needle fully down but Daz reckons we need to take the jets down to the mid 90s. I've skimmed one of the clutch plates and ordered a full range of Dellorto jets and will put her back on the Dyno in two weeks so I'll fill you all in then with the results.

The next outing is the CRMC event at Cadwell so I hope she's in a good mood before that!
Attached Images
glroberts99 is offline  
Sponsored Links
post #2 of 4 (permalink) Old 05-18-2016, 03:41 AM
Senior Member
emmevi125s's Avatar
Join Date: Sep 2006
Location: Melbourne, Australia
Posts: 1,762
Great to see a classic MV being raced.
emmevi125s is offline  
post #3 of 4 (permalink) Old 05-18-2016, 04:38 AM
Established Member
GTW36's Avatar
Join Date: Sep 2006
Location: FRANCE
Posts: 178
If the carbs are VHB square type, take a look to the starter plungers.

They have a rubber tip that dont like new unleaded fuel.

If the tip has not a quite flat and/or soft surface, it does'nt seal the starter jet and you are always running with the starter jet open...
If so, your carburation will be too rich, with black colored plug and it will be not possible to set correctly the carbs.

The difference between a man and a child is the price of his toys
GTW36 is offline  
Sponsored Links
post #4 of 4 (permalink) Old 06-12-2016, 05:24 AM Thread Starter
New Member
Join Date: Jan 2014
Location: Derby, England
Posts: 23

Thanks for the replies. The carbs are Dellorto UB types and after a trip to the Dyno man it was clear she was running much too rich. We had 105 jets in and after a number of runs, messing about with needle height and jet size, we settled on 96 main jets and middle notch. She now runs very sweetly, but.....

I rebuilt the clutch after some slipping issues at the end of last season and the extra thickness of thefricfion plates meant I couldn't get them all to fit in the basket. If I missed out a plate, she would slip in top gear at high revs and if I put in all the plates, she wouldn't disengage properly. I managed to get a compromise for the dyno testing (a whole 22 BHP at the rear wheel !!), but when I got to the CRMC meeting at Cadwell, she wouldn't let me find neutral with the engine running. Much head scratching, adjusting and messing around got me through scrutineeering but I couldn't get her noise tested because I needed her in gear to get the engine started and then couldn't keep her still as a) I couldn't get neutral and b) couldn't get the clutch to disengage enough to keep the bike stationary.

Then the electrics went and she discharged all three of my batteries within 3 minutes of starting.

So I'm waiting for new clutch pressure plates, springs and collets and have an electrical gremlin to kill.

Next outing will be the big CRMC three day event at Donington Park in August. Fingers crossed !!
glroberts99 is offline  

Quick Reply

Register Now

In order to use all of the features of the MVAgusta.net site, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome