Author Topic: Running out of puff  (Read 4141 times)

Offline A10Boy

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Re: Running out of puff
« Reply #15 on: 21.06. 2010 12:07 »
Adding two teeth to the engine sprocket is a whole different ball game from adding two to the gearbox.
Regards

Andy

1958 Super Rocket
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Yam XJR 1300

Offline Hubie

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Re: Running out of puff
« Reply #16 on: 22.06. 2010 03:44 »
I have been pondering that Andy and although I would have thought the overall result would be the same, perhaps it is not.  Can someone explain the difference to me??

Also I have one of those 4 spring triumph style clutch centres on my bike too, and could not get it off with a puller from an earlier attempt, what is the best way to do it, will applying some heat cause to much trouble?
1959 BSA Golden Flash
1956 Royal Enfield Super Meteor
1955 Royal Enfield 350 Bullet
2007 Harley Davidson Sportster 1200 Custom

The early bird gets the worm, but the second mouse get's the cheese!

Offline dpaddock

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Re: Running out of puff
« Reply #17 on: 24.06. 2010 21:34 »
Andy - given the typical sprocket teeth numbers involved, an incremental change to either of the driving sprockets will result in the same change in ratio.

Hubie - assuming you're using the centre extractor made for this job; screw it in, tighten the bolt and hammer it lightly. A little heat from a torch will help.

David
David
'57 Spitfire


Online bsa-bill

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Re: Running out of puff
« Reply #18 on: 24.06. 2010 22:10 »
I did have a spreadsheet someone kindly sent me that let you input the sproket sizes and it worked out the final ratio, can't find on this computer at the moment but the link below might be useful

http://www.mez.co.uk/mezporting/gearratio2.html
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline wilko

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Re: Running out of puff
« Reply #19 on: 24.06. 2010 23:34 »
That's a handy link Bill, i've kept that one. I don't have to use my brain!

Offline Hubie

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Re: Running out of puff
« Reply #20 on: 06.07. 2010 07:09 »
Had a good chance to give the bike a run today.  Got the original gearing back on it and it goes fine through the first three gears, but approach a hill and it is slower getting up there than my old bullet used to be.  Do I have a problem with carb settings or is it valve timing?  I am at a loss as to why it is fine through gears 1 to 3 and then has nothing up top in 4th.  After having a bit of a read on the forum I am confident my valve timing is not correct.  Next step is to learn how to check and adjust it.  Any help would be very much appreciated.

Cheers

Dave.
1959 BSA Golden Flash
1956 Royal Enfield Super Meteor
1955 Royal Enfield 350 Bullet
2007 Harley Davidson Sportster 1200 Custom

The early bird gets the worm, but the second mouse get's the cheese!

Online bsa-bill

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Re: Running out of puff
« Reply #21 on: 06.07. 2010 09:04 »
Difficult to see what could move though Dave however to check that the dots and dashs on the timing gears line up, means removing the outer timing case cover, the dynamo drive chain and large sprocket and then the inner timing case cover (four screw).
Then trun engine over ( could be up to 70 odd times ) to see if they all come together ( when they do the engine is at top dead centre)

To set it up so they do with out all that turning over -
best to remove the rocker box or screw out the tappets so the valves remain closed and remove spark plugs so your not fighting compression.
Then slide out the idler gear and turn the engine and cam shaft so that you can line up the dots on the crank pinion and idler gear and the dash on the cam gear and idler gear.
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Hubie

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Re: Running out of puff
« Reply #22 on: 06.07. 2010 09:28 »
Thanks Bill,

I am thinking that I am on the right track though.  I cannot think of what else could cause such a loss of power up top.  I have not checked it since I bought the bike either.

Cheers

Dave.
1959 BSA Golden Flash
1956 Royal Enfield Super Meteor
1955 Royal Enfield 350 Bullet
2007 Harley Davidson Sportster 1200 Custom

The early bird gets the worm, but the second mouse get's the cheese!

Online muskrat

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Re: Running out of puff
« Reply #23 on: 06.07. 2010 10:33 »
G'day Hubie,
                    Bill is correct, but to save un-doing the tappets turn the motor to bottom of stroke then remove the idler. Now turn the cam so the dash is pointing towards the center of the idler hole. Now turn the crank till the dot is towards the center of the idler hole. Now insert the idler and it should be only a little tweak to line it all up and push the idler home. The only way cam timing can be out is if it was set up wrong in the first place or the key in the cam or crank pinion has sheared.
 Double check the ign timing, if it's retarded it will spin in lower gears but loose out in top. Too advanced it will ping under load.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline Hubie

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Re: Running out of puff
« Reply #24 on: 06.07. 2010 11:37 »
Thanks mate,

Definately doesn't ping, and that's after i've advanced up the timing.  I have never checked the cam timing since I've had the bike so it's a least worth a check.
1959 BSA Golden Flash
1956 Royal Enfield Super Meteor
1955 Royal Enfield 350 Bullet
2007 Harley Davidson Sportster 1200 Custom

The early bird gets the worm, but the second mouse get's the cheese!

Offline Hubie

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Re: Running out of puff
« Reply #25 on: 09.07. 2010 06:38 »
Before I go this far, can someone tell me if I am on the right track?  I have the standard gearing, good power through gears 1-3 but in top when climbing a hill it runs out of steam and slows right down feeling suffocated/stifled.  Does it sound like cam timing?  I am happy with the ignition timing and can't get it to ping even though I have the timing advanced a tad more than standard.

Cheers,

Dave
1959 BSA Golden Flash
1956 Royal Enfield Super Meteor
1955 Royal Enfield 350 Bullet
2007 Harley Davidson Sportster 1200 Custom

The early bird gets the worm, but the second mouse get's the cheese!

Offline Stu55Flash

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Re: Running out of puff
« Reply #26 on: 09.07. 2010 07:13 »
Hubie

Have you checked the obvious stuff like air filter restrictions and full fuel flow to the carb?

Stu
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Online Brian

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Re: Running out of puff
« Reply #27 on: 09.07. 2010 07:26 »
What you describe Dave can be caused by the cam but also other things. Lack of top end can be due to carburettion or low compression, gearing etc. If you are sure all is well then maybe a check of the cam is worthwhile.

It is unlikely that the cam timing is wrong as has been stated as long as the dots and dashes line up then it should be right. You may have read that I had a issue with my Star Twin but I am certain that is due to a incorrect part that I will look into when that motor is apart again oneday.

If your problem is cam related it is more likely due to a worn cam or one that has been reground incorrectly. Just for an example here is a picture of a cam that had been ground incorrectly, it has lost 1/8" of lift and ground to the wrong profile. You will see that the heels have been completely removed and the timing on this cam was way out.

It is not too difficult to check the cam timing and you only need a couple of basic items the main one being a degree disc. It also helps if you know what cam is in the motor but that is not essential. You do need to understand how to read the degree disc, ie. before top dead centre, after bottom dead centre etc. Your motor will probably have either a 334 or a 356 cam. The figures for these are as follows.
67-334   inlet      opens 30d BTDC and closes 70d ABDC
            exhaust  opens 65d BBDC and closes 25d ATDC

67-356   inlet      opens 42d BTDC and closes 62d ABDC
            exhaust  opens 67d BBDC and closes 37d ATDC
  

Offline Hubie

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Re: Running out of puff
« Reply #28 on: 09.07. 2010 07:32 »
Thanks Brian,

I have a monobloc on a super meteor i might try on it to rule out carburetion.  It is fine and the meteor pulls like a train.  Then I will go to a motorbike mate and have him show me how to properly check the cam timing.

Cheers,

Dave.
1959 BSA Golden Flash
1956 Royal Enfield Super Meteor
1955 Royal Enfield 350 Bullet
2007 Harley Davidson Sportster 1200 Custom

The early bird gets the worm, but the second mouse get's the cheese!

Online bsa-bill

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Re: Running out of puff
« Reply #29 on: 09.07. 2010 11:26 »
Hubie I can't see anywhere you say what gear you have on the gearbox, the reason I ask is because  with a 24 tooth on the engine ( which you have now changed) and the rest of the gears standard, I'm thinking it would be quite feat to kick it over.
Anyway some overall ratio choices assuming you have a 19 tooth on the gearbox

standard   21 engine, 43 clutch, 19 gearbox, 42 wheel = overall ratio 4.53
Yours       24, 43, 19, 42 = overall 3.96
Sidecar     21, 43, 18, 42 = overall 4.78 or 20, 43, 19, 42 = overall 4.75
Yours now 22, 43, 19, 42 = overall 4.32

mine to get just a tad more acceleration 22, 43, 18, 42 = 4.56

4.32 is still a good bit higher than standard ( 4.53 ) a difference of 0.21, consider that sidecar ratio is a difference of 0.22 or 0.25, so you are still as much higher than side car gearing is lower, also consider that added to all this is you gearbox ratios which help your engine in the lower gears but by the time you get to top the full effect of your overall ratio will become more pronounced

As per usual my maths are open to scrutiny
(another pet hate - why all of a sudden has it become MATH in place of MATHS)
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco