Britbike forum

Classic British SparesKlempf British PartsBaxter CycleBritBike Sponsor SteadfastCyclesThe Bonneville ShopLowbrow CustomsSRM EngineeringGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supply

Upgrade your membership: Premium Membership Gold Membership


New Sponsor post
Cyber Monday Sale - 10% off at The Bonneville Shop
by The Bonneville Shop - 11/29/21 5:34 pm
New FAQ post
How to find my own threads?
by reverb - 11/20/21 3:55 pm
Manuals on DVD - Buy 4 for 3
All 4 DVD Manual
Member Spotlight
kommando
kommando
Scotland
Posts: 11,449
Joined: December 2004
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Top Posters(30 Days)
NickL 79
Rohan 77
Top Likes Received (30 Days)
kevin 22
Newest Members
old ion limey, muzz750, Motorcycles and Art, SteveDee, Gus_Carrero
11,924 Registered Users
Who's Online Now
8 members (bsalloyd, BSA_WM20, 2ndchildhood, DJinCA, Robbo6, BrizzoBrit, Mark Z, kevin), 21 guests, and 19 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
#861751 10/26/21 7:58 pm
Joined: Sep 2021
Posts: 5
L
Looping Offline OP
Britbike forum member
OP Offline
Britbike forum member
L
Joined: Sep 2021
Posts: 5
Hello everyone

I have a vintage flat track project in a homemade frame. I have an A65 thunderbolt engine almost complete with lightened vilo and dual carb head.

SRM do not have any more big bore kit so this engine will stay 650cc

i am looking for "timing side bearing conversion" I believe I have read all the subject matter on this subject but if certain some people have opinions or even photos on the modificationon modification for lubrication I am a taker

If some people have information to share on the preparation of these engines for the flat track, I will be delighted.


thanks
Lucas

British motorcycles on eBay
Joined: Aug 2001
Posts: 5,459
Likes: 62
R
Britbike forum member
Offline
Britbike forum member
R
Joined: Aug 2001
Posts: 5,459
Likes: 62
You may be better off with a 650. A lot of BSA’s that worked well on a flat track were 650’s.

A 360 degree twin has to do a balancing act between power and traction on dirt. Too much power, you spin coming off the corners. You also gear to run the entire straight….same reason, you need traction on corner exit.

Don’t lighten the crank, stock weight works. A heavy billet crank, if you can find one, works better. Best rods you can afford.

Don’t be tempted to go too high on compression. You lose low end with high compression. Likely 32mm carbs will be big enough.

Single row primary using Triumph/A10 4 spring clutch improves reliability of the primary. Dirt track beats the snot out of a BSA primary.

Just don’t overbuild the engine for power. You will likely be disappointed


Never underestimate the human ability to elevate stupid to a whole new level!.
Joined: Apr 2005
Posts: 2,908
Likes: 54
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,908
Likes: 54
You can use a straight heavy series roller and put a bearing outside the alternator and one behind the clutch, then the triplex will stay together and you have end float in the crank covered. There is actually a L/hand thread bicycle pedal mount you may be able to screw on the end of the crank and make an oil feed spigot. You can tee a gage and oil line off a Tee at the oil pressure switch port. Run a pipe and oil into a fitting in the inner case and into an oil seal area on the end of the crank. You do not need 750cc just a good head. I have some posts on that on the BSA forum and here if you can decipher the ramblings.

You could use 32mm carbs or 34mm, just that 34s kick in pretty hard when right open. It needs balancing so you can hold onto it. 34mm give good response from low rpm which is what Rich is recommending. But high flow and speed deliver that with 34s, low speed and bad port shape doesn't.

NKIS 30.
[Linked Image from i.postimg.cc]

Bearing and mount. This means at rpm the alternator will not run into the stator. And the chain will run in line.

[Linked Image from i.postimg.cc]

You do not need the 5speed but you need the 3rd mainshaft bearing. Ed V has them and high quality pistons at a good price, MAP have high speck light steel rods.

[Linked Image from i.postimg.cc]

It needs balancing for rpm (factory raced with 56%) and good valve springs SRM have race springs that shimmed right will allow 9,000, not that those rpm should be necessary, they are not overly heavy.

Depending on the head, basically the std clutch will not work. It needs the heaviest race springs you can get and the narrow 7 plate kit or something similar and probably a packer, plus auto trans fluid in there.

[Linked Image from i.postimg.cc]

This head is for std valves which would be fine, but 42mm give you more flow and lots of drive. I'm using these carbs on the road and flow can be around 53% more than stock so the bottom end can be pretty much stock cam and compression and still have a very strong responsive engine.

It would need good breathing filters.

[Linked Image from i.postimg.cc]


mark
Joined: Sep 2021
Posts: 5
L
Looping Offline OP
Britbike forum member
OP Offline
Britbike forum member
L
Joined: Sep 2021
Posts: 5
Thanks a lot for your informations, i will study all this.

If someone has the weight of the original crankshaft I could compare with mine.

I am also looking a technical instruction for rebuilt valve seat do you have this ?

Thanks

Lucas

Joined: Apr 2005
Posts: 2,908
Likes: 54
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,908
Likes: 54
Yet to machine this but Ben found a pedal mount commonly available for push bikes with the correct left hand thread. It needs to be the correct length but can make a spigot for the crank that screws on the end. I've had these made before but this looks like an easy starting point.

[Linked Image from i.postimg.cc]


mark
2 members like this: PEH, NickL
Joined: Jun 2013
Posts: 115
Likes: 2
P
PEH Offline
Britbike forum member
Offline
Britbike forum member
P
Joined: Jun 2013
Posts: 115
Likes: 2
Hi Mark, Would you have any jetting/needle info for the flatslide carbs, i have a pair of 32's id like to fit on an A65 Trackmaster flattracker i built.

Joined: Apr 2005
Posts: 2,908
Likes: 54
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,908
Likes: 54
The pwk34s I use have 150 main jets. But they a 34s on a head that flows 167cfm.


mark
Joined: Jun 2013
Posts: 115
Likes: 2
P
PEH Offline
Britbike forum member
Offline
Britbike forum member
P
Joined: Jun 2013
Posts: 115
Likes: 2
Thanks Mark, Is there a needle that works best, or just the one that came with the carb?

Joined: Apr 2005
Posts: 2,908
Likes: 54
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,908
Likes: 54
The std one works, I have different ones fitted. I imagine the porting effects it. But in any case setting up a wide band oxygen sensor and air fuel gauge could establish the settings fast. And the road isn't a great place to be looking at that. Ben has one on his BSA and it could be easier to read as it isn't that bright.

On a dyno it would have one up the exhaust end as well to compare and would be more ideal. Ben's is very fast acting and dialing in 12.5% for wide open sort of easy, and at other points, but some places are lean or rich and a bit hard to pin point throttle position. A dyno would be the place after getting it to run through the range. and marking the twist grip. Then recording the readings at each point.

I really need to do that with the Firebird so I know exactly what works with the 34pwk and this type of port. But the 150 main seems pretty good.


mark
1 member likes this: PEH
Joined: Jun 2013
Posts: 115
Likes: 2
P
PEH Offline
Britbike forum member
Offline
Britbike forum member
P
Joined: Jun 2013
Posts: 115
Likes: 2
Thanks again Mark. I have a dyno i use just up the road at Mallory Park, I will give it a go.

Joined: Sep 2021
Posts: 5
L
Looping Offline OP
Britbike forum member
OP Offline
Britbike forum member
L
Joined: Sep 2021
Posts: 5
I come to give you some news.
On your advice, I received MAP steel rod and I am about to order ED V pistons.
For the lubrication system, the person who sold me the engine invited me to come and see his modifications to these engines.
I took some pictures here.
thanks to her
[Linked Image from zupimages.net]
[Linked Image from zupimages.net]
[Linked Image from zupimages.net]
[Linked Image from zupimages.net]


We use a bearing ref NKI 38/20 XL and will start machining and assembly next week

concerning the head engine, a cam to advise me?
I was thinking of using an spitfire cam, any reviews?
I am also thinking of using Mikuni vm 32.
I read all the subject of Mark Parker on the cylinder head but I am a little lost, would you have any advices and photos on the preparation of a cylinder head for 32mm carbs and which diameter of exhaust would you use?

I have made good progress on the frame and I will be able to concentrate on the engine.
Thank you for your answers
Lucas
[Linked Image from zupimages.net]
[Linked Image from zupimages.net]

Joined: Jan 2004
Posts: 5,186
Likes: 122
D
Britbike forum member
Offline
Britbike forum member
D
Joined: Jan 2004
Posts: 5,186
Likes: 122
Instead of the external oil line you might consider moving it inside. You can intersect the pressure side down to the OPRV and put in a post to the outer timing cover then route it to your end feed boss. A little safer than having a low external line on a flat track bike.
[Linked Image from live.staticflickr.com]
[Linked Image from live.staticflickr.com]

Joined: Sep 2016
Posts: 16
B
Britbike forum member
Offline
Britbike forum member
B
Joined: Sep 2016
Posts: 16
Hi. Very interesting build.I love the flat track look. Im in a similar situation working on an end feed system. On your friends engine Can you tell me how the oil seal housing on the end of the crank is held in place?

Thanks Ben

Joined: Sep 2021
Posts: 5
L
Looping Offline OP
Britbike forum member
OP Offline
Britbike forum member
L
Joined: Sep 2021
Posts: 5
it's welded

[Linked Image from zupimages.net]

Last edited by Looping; 11/28/21 4:50 pm.
Joined: Sep 2021
Posts: 5
L
Looping Offline OP
Britbike forum member
OP Offline
Britbike forum member
L
Joined: Sep 2021
Posts: 5
DMadigan
I don't think I have a problem with the external passage, the passage will be made in flexible

Joined: Jan 2014
Posts: 1,761
Likes: 208
N
Britbike forum member
Offline
Britbike forum member
N
Joined: Jan 2014
Posts: 1,761
Likes: 208
Is the cover still straight?......welding is usually bad news.
The easiest way of obtaining a hidden oil supply is to drill
the gallery through and use a hollow oil pump stud then
bring it up through the timing cover. But there are so many
different ways to do this mod. The feed should be at least
4mm id tube really, taking the supply from the switch has
a restriction and will need drilling out.
Don't forget to blank off the main bearing feed or just use
plug with a 1mm hole in it to supply the bearing.


Moderated by  Allan G 

Link Copied to Clipboard
Job CycleBritish Cycle SupplyMorries PlaceKlempf British PartsPodtronicVintage MagazineBSA Unit SinglesBritBike SponsorBritish Tools & FastenersBritBike SponsorBritBike Sponsor






© 1996-2021 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5