Bimota Forum Forum Index Bimota Forum
Forum for Bimota Owners and Riders
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  

YB7 Not Revving out
Goto page 1, 2  Next
 
Post new topic   Reply to topic    Bimota Forum Forum Index -> YB Series
View previous topic :: View next topic  
Author Message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Wed Apr 04, 2018 2:59 am    Post subject: YB7 Not Revving out Reply with quote

Hi All
Been in hibernation for a while as I worked through some issues with the YB7 (fuel pump and dirty carbies) and other bikes got in the queue ahead of it. But I have finally ridden it but not to the full potential. The bike hits a wall at 5500 and will not go past. I'll have to take the airbox off again and check the main jets but keen to hear if anybody has any other suggestions as to what the issue may be. The EXUP valve cycles but I will get underneath and check the movement of the cycle is right and cables are adjusted correctly.

Am I correct in my understanding that YB7's run Mikuni 38mm flatslides? Before I go fiddling with jets it would be good to know what the base jet size is.

Thanks for the help.
PK
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
Admin
Site Admin


Joined: 22 Oct 2007
Posts: 503
Location: Stafford, UK

PostPosted: Wed Apr 04, 2018 9:39 am    Post subject: Reply with quote

Hiya

I wouldn't expect the exup issue to stop it suddenly at those revs. I would expect it to slowly loose umph.

Carb wise, not sure but 38mm sounds WAY too big for a 400. Quick google suggests 32mm Mikuni carbs. I would expect that they are CV carbs rather than slide carbs. And probably he source of the running issue.

Katy
Back to top
View user's profile Send private message Send e-mail
Jonny B Bad



Joined: 05 Dec 2009
Posts: 408
Location: NE London

PostPosted: Wed Apr 04, 2018 10:02 am    Post subject: YB7 Reply with quote

Sounds like it's running rich. I would look for wear on needles. If there is visible wear, you probably want new needles and needle jets.
_________________
What, Jonny's gone!
Back to top
View user's profile Send private message
Evilchicken0



Joined: 12 May 2010
Posts: 2791
Location: London

PostPosted: Wed Apr 04, 2018 9:36 pm    Post subject: Reply with quote

32mm smoothbores on tbe fzr 2tk, the engine is the FZR400R SP its a 1WG.
Could be somebody got the main and idle jets crossed over ... that woulx normally be 8000rpm though. Kd say to clean the carbs again anc check theyre balanced. The Exup isnt a bad call chcek the servo is opening and hasnt sheared and teeth on the gear, make sure the cables arent too tight you should be able the squeeze the cables together a bit.
_________________
Don't read everything you believe
Back to top
View user's profile Send private message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Thu Apr 05, 2018 1:42 am    Post subject: Reply with quote

Thanks guys.

I thought about the jet mix up so I'll check that. I have a new set of main jets at stock size per the FZR manual. The reason for my uncertainty is that while the FZR runs 32mm I did read that the YB7 was rejetted to allow for the Bimota back end of the exhaust which was less retsricted than stock. Now how this has translated to my bike is an unknown so when I have the fairing and stuff off (again) I'll take a look. I'll try to remember some pictures too....

Cheers

Paul
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
Evilchicken0



Joined: 12 May 2010
Posts: 2791
Location: London

PostPosted: Thu Apr 05, 2018 2:06 pm    Post subject: Reply with quote

The can doesn't make much difference, it's the exup that governs the exhaust, at least up to 8000 rpm.
Remember it's the 2TK model engine and carbs .... the closest model after that is the 3EN (1988 + 89) but always look for the model codes rather than the year.
_________________
Don't read everything you believe
Back to top
View user's profile Send private message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Sat Apr 14, 2018 11:04 am    Post subject: Reply with quote

Evening all.
So had the carbs off the YB7 today. The model number on the carby was 3EN-59710. I installed a set of 87.5 main jets per the book and now it revs over 5,500 but has no bottom end. My Kawasaki G7 has more torque!

Now I presume I have put the mains on the correct post (the carb picture in the parts book is rubbish) - I stupidly didn't look down the tube to make sure (it was the 5th bike I'd worked on today with a slight hangover-goose!). So I put them on the post that is the shorter of the two. Is this correct?

Anyway I couldn't read the numbers on any of the jets (I checked the pilots to make sure they were the same number but couldn't read them) but the new ones were quite different in physical size to the old ones.

I think I'll replace the pilots anyway and balance the carbs. So it all comes off again - fortunately it has to be the easiest bike to do carbs on (try a GSXR-750 if you're a masochist)

The EXUP cables were all good.
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Sat Apr 14, 2018 11:07 am    Post subject: Reply with quote

Oh and the EXUP servo was working fine - I could watch it adjusting with the throttle position.

Another thing I forgot to mention was it gives a stutter off closed throttle then pick up fine (just no torque).
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Sat Apr 14, 2018 11:21 am    Post subject: Reply with quote

OK here is the really dumb question - do the pilot jets and main jets on this bike look the same? I was just poking around on the Mikuni website and the pilots look completely different. The only one that looked similar was a jet ski pilot. All the other pilots were long screw in types.
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
rpo83



Joined: 28 Oct 2008
Posts: 294
Location: Melbourne, Australia

PostPosted: Sat Apr 14, 2018 11:31 am    Post subject: Reply with quote

Hi Pkay, if you are interested, a mate of mine is a bike mechanic in Logan City, he would without doubt, be the best bike mechanic out there.

He has a dyno and is very thorough, he primarily works word of mouth, you can look him up on facebook... Barry’s Motorcycle Garage - SEQ...
_________________
Cheers

Steve

1988 YB5
1995 SB6
Back to top
View user's profile Send private message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Sat Apr 14, 2018 10:26 pm    Post subject: Reply with quote

Thanks Steve
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Sun Apr 15, 2018 8:39 am    Post subject: Reply with quote

PROBLEM SOLVED - woo hoo! First time since buying it that I got to ride it properly. Deceptive as you don't realise how fast you're going. And so light - just tips in.

So, turns out that the previous owner had put larger jets in the middle mains. All the others (main and secondary) were the same size. So put my new stock mains in, made the secondary's all the same size, balanced the carbs (they were pretty close anyway) and there you have it!

Thanks again for the suggestions and tips
PK
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
pkay



Joined: 16 Dec 2016
Posts: 72
Location: Brizvegas

PostPosted: Sun Apr 15, 2018 8:39 am    Post subject: Reply with quote

PROBLEM SOLVED - woo hoo! First time since buying it that I got to ride it properly. Deceptive as you don't realise how fast you're going. And so light - just tips in.

So, turns out that the previous owner had put larger jets in the middle mains. All the others (main and secondary) were the same size. So put my new stock mains in, made the secondary's all the same size, balanced the carbs (they were pretty close anyway) and there you have it!

Thanks again for the suggestions and tips
PK
_________________
pkay
YB7 and many other assorted Euro and Jap bikes and one Triumph.......
Back to top
View user's profile Send private message
rpo83



Joined: 28 Oct 2008
Posts: 294
Location: Melbourne, Australia

PostPosted: Sun Apr 15, 2018 9:56 am    Post subject: Reply with quote

Great news, everything i've read about the TB7 is very positive, i was trying to talk the Mrs, into buying on for herself.... she was on to my cunning plan.. One review i read said it was without doubt the best Bimota for road riding...
_________________
Cheers

Steve

1988 YB5
1995 SB6
Back to top
View user's profile Send private message
brian



Joined: 22 Aug 2011
Posts: 2692
Location: QLD, Australia

PostPosted: Sun Apr 15, 2018 10:06 am    Post subject: Reply with quote

Good news. A well tuned 400 can be very rewarding. I race a CBR400RR and it's a real hoot on a track. I'd love to have YB7 to race, but at least with the CBR I don't mind craashing Laughing
_________________
Current motorcycles - '99 Bimota DB4, '96 Bimota SB6, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, ‘94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, ‘61 BSA A10 650
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    Bimota Forum Forum Index -> YB Series All times are GMT + 1 Hour
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group

The Bimota Forum has no official connection to Bimota S.p.A.. We just ride or are interested in their motorcycles and support the brand. All trademarks are acknowledged