Latest topics
» Trials sprocket
Yesterday at 8:15 pm by peter@dunfordconstruction

» Cruiser oil.
Yesterday at 7:37 pm by kerabo

» F/B Falcon
Yesterday at 2:43 pm by peter@dunfordconstruction

» Rubber gaiters
Yesterday at 9:04 am by FBKev

» Buckled flywheel
Sun Nov 11, 2018 8:20 pm by Dadzee

» Cables Cruiser 39.
Sun Nov 11, 2018 3:25 pm by kerabo

» cruiser 45 carburettor
Sat Nov 10, 2018 4:40 pm by piston 197

» Part needed
Fri Nov 09, 2018 7:47 pm by kerabo

» Hello - new owner 1958 Crusier 2T, bike registration help
Fri Nov 09, 2018 3:46 pm by chrisbwy


1959 FB trials help

Go down

1959 FB trials help

Post  Algernon on Tue Aug 18, 2015 11:28 am

Hi guys I have almost completed the restoration and today I took the bike out for its first test ride. Everything seems perfect until I reach 4th gear. When I hit 4th I lose all acceleration and simply can only maintain the speed I was going when I changed. Can anyone offer advice on what I should check. I was not using any choke at the time and the bike was at the correct temperature

here is the progress








thanks again
regards James

Algernon

Posts : 18
Join date : 2015-04-21

Back to top Go down

lack of acceleration in top

Post  piston 197 on Tue Aug 18, 2015 12:22 pm

Sounds like you just have a high top gear, if it accelerates ok in the first 3 gears, the trials box uses low ratio first second and third with high ratio top for road work, hence a big jump from 3rd to 4th, making 4th seem like an overdrive. You may need to rev it high in 3rd before changing into top to get it far enough into the power curve to allow it to accelerate ? back sprocket option on rear wheel was 56 teeth with options up to 64, is yours smaller than this
JH
avatar
piston 197
Moderator

Posts : 4090
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: 1959 FB trials help

Post  Algernon on Tue Aug 18, 2015 1:28 pm

I have 54 teeth on the rear sprocket

Algernon

Posts : 18
Join date : 2015-04-21

Back to top Go down

Re: 1959 FB trials help

Post  Algernon on Tue Aug 18, 2015 1:33 pm

the next thing Im going to try is to open the choke when I hit 4th gear and see if I get acceleration then I know to change the jetting.

Algernon

Posts : 18
Join date : 2015-04-21

Back to top Go down

open the choke ??

Post  piston 197 on Tue Aug 18, 2015 1:39 pm

Why have you got the choke closed ? surely as soon as the engine is warm the choke should be open anyway ?? you will get poor acceleration with the choke closed ? are you confirming open with closed ?
Choke is off when slide is raised  ( tight cable)and closed when in the lowest position  slack cable)
In your first picture choke is in the off/open position ( normal running/tight cable) if you move it from this position you are closing it/putting choke on )
JH
avatar
piston 197
Moderator

Posts : 4090
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: 1959 FB trials help

Post  Algernon on Tue Aug 18, 2015 4:08 pm

sorry wrong use of term, I have yet to even try using the choke as it has not been necessary. The choke has always remained open

Algernon

Posts : 18
Join date : 2015-04-21

Back to top Go down

Trials

Post  kerabo on Tue Aug 18, 2015 4:17 pm

It looks good well done.
As said it could be gearing or you have a big loss of power  to start with. providing its got a standard gearbox sprocket it should pull a 54 tooth rear.
Mine using a 32A engine has 60t rear.
Don't the forks hit the tank in full lock?

Ken
avatar
kerabo

Posts : 2480
Join date : 2008-02-11
Age : 68
Location : Falcon 87..1936 Cruiser 39. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

tank stops

Post  piston 197 on Tue Aug 18, 2015 4:24 pm

The tank is the model 85 type which does not have the lock stop dents of the 83, the front mounts are longer and the front of tank is further back, the hex bars protruding from the bottom yoke should hit the frame first and prevent the forks touching the tank ?
JH
avatar
piston 197
Moderator

Posts : 4090
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: 1959 FB trials help

Post  Algernon on Tue Aug 18, 2015 4:36 pm

there is no contact with the tank in full lock, the engine is practically brand new and the bike has a large deal of compression so I dont think its power related.

Algernon

Posts : 18
Join date : 2015-04-21

Back to top Go down

sprocket

Post  andy-s on Tue Aug 18, 2015 8:35 pm

Hi , its well worth trying a larger rear sprocket . I had a the same problem on a 4 speed falcon,(but In my case i don't think these bikes were made with the larger gentleman in mind) got a larger sprocket from VS and now at least I can stay in 4th ok.
avatar
andy-s

Posts : 124
Join date : 2012-09-17
Age : 51
Location : Frome

Back to top Go down

Re: 1959 FB trials help

Post  kerabo on Tue Aug 18, 2015 8:41 pm

Algernon wrote:there is no contact with the tank in full lock, the engine is practically brand new and the bike has a large deal of compression so I dont think its power related.
Yes but even if the engine is good it only needs the timing ir carb to be out to loose lots of power .
You was saying you never need choke Thats an indication itsca little rich.
What size sprocket would it originally have had .
My 200cc falcon 87 pulls a 52 tooth on an 18" wheel easy .
Regards Ken
avatar
kerabo

Posts : 2480
Join date : 2008-02-11
Age : 68
Location : Falcon 87..1936 Cruiser 39. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

Re: 1959 FB trials help

Post  Algernon on Wed Aug 19, 2015 5:12 am

I weigh 67 kg so I don't believe I could be weighing it down, Im running a mixture of 30:1 with a good quality castrol mineral 2 stroke oil.

Algernon

Posts : 18
Join date : 2015-04-21

Back to top Go down

mixture

Post  piston 197 on Wed Aug 19, 2015 6:11 am

If you are running @ 30 to 1 the viscosity of the mix will be thinner than if it was 20 to 1 i.e. more fuel will pass through the jet at a given time making it richer. I presume you have compensated with jet sizes for this mix ? might be why you do not need choke from cold ? if not a change to 20 to 1 might be worth trying. If you google the Queens university Belfast two stroke trials with fuel mix for Greeves it goes against what you would expect ! more power was produced at 16 to 1 and power fell off as the mix was diluted , although I am sure smoke increased as did the propensity for fouling plugs, needless to say they compensated jets to suit mixture
JH
avatar
piston 197
Moderator

Posts : 4090
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

FB Trials 83 original spec

Post  FB vincent on Wed Aug 19, 2015 3:46 pm

For info, the original spec (1958) for the gearing and rear sprocket was quoted as follows:

Rear wheel sprocket: Standard 56, options 58 and 60 (Cruiser 80 was 52)

Overall gear ratio (top) 8.0 (Cruiser 80 was 5.9)

FB vincent

Posts : 665
Join date : 2009-01-20
Location : Hertfordshire

Back to top Go down

Re: 1959 FB trials help

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum