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tommo-sb6
Joined: 08 May 2013
Posts: 36
Location: United Kingdom
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 Posted: Wed May 22, 2013 3:00 pm Post subject: low compression in 1 and 2 |
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hello folks,
recently bought Bimota sb6 low mileage 5450 with history to back it up so i obviously thought no worries there especially with gixxer 11 engine, The old lass did smoke slightly but sounded sweet and i was hoping the smoke was with it not been run for a couple of years which it still might be, Anyway ive done a compression test, cold engine with throttle wide open to let as much air in as possible number 1 was 90 psi number 2 was 120 psi number 3 and 4 was 150 psi surely if the rings are worn then all cylinders would be quite low, could it be the valves not seating correctly with wrong clearances, I was going to have the engine out anyway to check it over but it would be nice to have someone elses thoughts though...I would be pissed off if a fellow biker had sold it knowing that something was wrong...kindest regards Tommo |
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Evilchicken0
Joined: 12 May 2010
Posts: 2996
Location: London
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| Posted: Wed May 22, 2013 5:30 pm Post subject: |
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Try it "wet". add a squirt of engine oil down the plug hole then repeat the compression test. If the comp is noticably higher than the previous result it's an indication of worn rings / bores. The oil forms a tempory seal around the rings giving you a higher reading.
If it's no better after a wet compression test then suspect the valves.
Make sure the comp tester is properly sealed when you test - if it's leaking it will be low.
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Vince186
Joined: 23 Mar 2012
Posts: 636
Location: Nijmegen (Netherlands)
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| Posted: Wed May 22, 2013 7:37 pm Post subject: |
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As EC says try it “wet” and see what happens.
But speaking from experience if the bike had stand still for a long time it can take a while for she start to runs better. It’s possible that the piston rings sticking.
Valve clearance check is always good, it certainly can’t hurt.
If you check the clearance measure the cam height. Than you know which cams are installed.
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vince
A person who never made a mistake never tried anything new. Albert Einstein |
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JRH
Joined: 21 Jan 2013
Posts: 223
Location: West Mids/North East
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| Posted: Wed May 22, 2013 8:01 pm Post subject: |
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| Head gasket between 1 and 2....? |
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Mako
Joined: 17 Dec 2011
Posts: 141
Location: Reggio Emilia, Italy
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| Posted: Wed May 22, 2013 8:13 pm Post subject: |
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my first check would be to repeat the test without carbs diaphragms... if they are stuck when you are at full throttle (compression test should be done wit full throttle opening) the air inlet would be much less then ather cylinders.... less air-less compression.
step 2 wet test
step 3 engine off and surgery games
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Honda CB450K1 - CB750K2 - CB500K1 - RC30 - Ducati 750SS - Bimota SB6 |
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tommo-sb6
Joined: 08 May 2013
Posts: 36
Location: United Kingdom
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| Posted: Wed May 22, 2013 9:48 pm Post subject: |
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| Vince186 wrote: |
As EC says try it “wet” and see what happens.
But speaking from experience if the bike had stand still for a long time it can take a while for she start to runs better. It’s possible that the piston rings sticking.
Valve clearance check is always good, it certainly can’t hurt.
If you check the clearance measure the cam height. Than you know which cams are installed. |
Thanks for all the help and recommendations, Vince which cams did they use. The head gasket sounds a huge possibility as 3 and 4 are superb compression and 1 and 2 arent surely if the rings was getting worn then all 4 would be quite low, you would think all 4 going up and down at the same time they would wear out evenly, but iam taking in all what you experienced lads are telling me and i will be checking everything out that you are saying..many thanks to you all Tommo |
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Evilchicken0
Joined: 12 May 2010
Posts: 2996
Location: London
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| Posted: Wed May 22, 2013 10:42 pm Post subject: |
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Why not take the carbs off and test it.
Don't worry about the cams - Bimota took the 100 bhp limit a bit seriously and changed the cams to suit. All the cams are stamed on the left (generator) side but of all the bikes out there mine seems to be the only one.
Your bike is low mileage so it must have stood for a while. That could mean the bores have dried out or when the bike was started after a lay up the cylinders didn't have any oil put down them.
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brian
Joined: 22 Aug 2011
Posts: 3790
Location: Australia
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| Posted: Thu May 23, 2013 1:44 am Post subject: |
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Being such a low mileage bike, and having sat for a while, If it were mine i'd give it a good check over, change the fuel and oil and put 1000 miles on it. Then check the compression again. Just my opinion.
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '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, '89 ZXR750, '91 Ducati 851 |
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vort28
Joined: 22 Mar 2010
Posts: 2194
Location: Northwest , UK
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| Posted: Thu May 23, 2013 8:49 am Post subject: |
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| Could just be the way it was sat? Chances are some of the valves had to be open and maybe these just not sealing correctly or can't due to corrosion/debris on the seat/valve. |
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tommo-sb6
Joined: 08 May 2013
Posts: 36
Location: United Kingdom
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| Posted: Thu May 23, 2013 8:49 am Post subject: |
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| Evilchicken0 wrote: |
Why not take the carbs off and test it.
Don't worry about the cams - Bimota took the 100 bhp limit a bit seriously and changed the cams to suit. All the cams are stamed on the left (generator) side but of all the bikes out there mine seems to be the only one.
Your bike is low mileage so it must have stood for a while. That could mean the bores have dried out or when the bike was started after a lay up the cylinders didn't have any oil put down them. |
Oh heck i never thought of that, That could be a huge possibility not everyone would think of putting some oil down the plug hole, I really hope thats not the case, Brian if i hadnt got it so far stripped down then thats what i would have done, But as ive got it to a point where all i have to do is undo the engine mounts then i may as well take the lump out and check it over, Carbs off then re- check compression then it looks like engine out...thanks everyone..Tommo |
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Hursty
Joined: 29 Aug 2012
Posts: 319
Location: New Zealand
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| Posted: Thu May 23, 2013 9:58 am Post subject: |
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Welcome to our wonderful world of Bimota ownership  at least I got a few rides in on mine before disassembly 
Enjoy the journey it will be worth it in the end
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Hursty from kiwi land  |
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tommo-sb6
Joined: 08 May 2013
Posts: 36
Location: United Kingdom
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| Posted: Thu May 23, 2013 10:37 am Post subject: |
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| Hursty wrote: |
Welcome to our wonderful world of Bimota ownership at least I got a few rides in on mine before disassembly
Enjoy the journey it will be worth it in the end |
Aye up mate, I only stripped it to bloody clean the old girl and get her looking nice but its looking like she wont be back together for a few weeks, but not the end of the world, Like you say Hursty its all part of owning older bikes, Ive got an old gs1000 and an old z650 all of which needs love care and attention all the time, I had 2 old z1300s and getting parts for them old beasts was a nightmare but they all have character unlike my 2013 fireblade which i might soon be selling as I am bored of it already...kindest regards Tommo |
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Vince186
Joined: 23 Mar 2012
Posts: 636
Location: Nijmegen (Netherlands)
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| Posted: Thu May 23, 2013 6:57 pm Post subject: |
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Keep us informed about the compression results.
About the cam height.
According to the Suzuki manual there are three sets of cams possible.
It has nothing to do with you compression problem but it is just nice to know what’s installed.
If you check the valve clearance it takes 1 minute extra to measure the cam height.
To satisfy my curiosity, I would like to know.
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vince
A person who never made a mistake never tried anything new. Albert Einstein |
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tommo-sb6
Joined: 08 May 2013
Posts: 36
Location: United Kingdom
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| Posted: Thu May 23, 2013 7:10 pm Post subject: |
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| Vince186 wrote: |
Keep us informed about the compression results.
About the cam height.
According to the Suzuki manual there are three sets of cams possible.
It has nothing to do with you compression problem but it is just nice to know what’s installed.
If you check the valve clearance it takes 1 minute extra to measure the cam height.
To satisfy my curiosity, I would like to know.
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Hello Vince,
many thanks for that info, I will get mine measured once i get stuck into it and let you know the results...kindest regards Tommo |
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Evilchicken0
Joined: 12 May 2010
Posts: 2996
Location: London
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| Posted: Thu May 23, 2013 11:25 pm Post subject: |
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Bimota SB6 manual says
So if your cams have A and B stamped on them they're French and give 100 bhp
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