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#687157 - 03/07/17 8:17 pm 1970 Thunderbolt  
Joined: Nov 2011
Posts: 77
GreenMonster Offline
BritBike Forum member
GreenMonster  Offline
BritBike Forum member

Joined: Nov 2011
Posts: 77
NH
Hello Everyone:

It has been a long time since I have been around I hope everyone is well I missed you guys.

Anywho I am looking for some experienced feedback, I am finally building my matching #s 70 A65 engine and I am thinking about going with the following

This is a stock head with KibbleWhite valves, guides and keepers with mild port work and an AMAL Premier 930 Concentric.

The Jug is stock bore with 9:1 JCC pistons and Rekin rings.

The bottom end will have the big end conversion by E&V Engineering
coupled to a set of MAP/ Manley 4340 forged H beam rods and, a Johnson Cams Sifton 391 grind.

Planning keeping stock gearing.

Limited road use at her age she just gets out on the occasional summer night to terrorize the sport bike kiddies

Thanks Guys


Never Allow The Radical Views Of The Few To Infringe On The Constitutional Rights Of The Many
#687650 - 03/11/17 3:44 pm Re: 1970 Thunderbolt [Re: GreenMonster]  
Joined: May 2013
Posts: 4,232
Allan Gill Online sleepy
Allan Gill  Online Sleepy



Joined: May 2013
Posts: 4,232
Rotherham - S. Yorkshire
Hi Green Monster, this might be better posted in the BSA section, if you like I can move it for you?

Personally I wouldnt fit this cam. For a bike you want to ride on the street, you dont want a cam that has good midrange. This cam is mainly for high end rpms and could make it a pig to ride on the street, also having single carb it will never breath as well as a twin carb at high revs (so again not suited to the cam)

The SRM race cam is a good alrounder and will rev too, but whilst it has low end grunt... your pillion needs to hold on well as its hard to keep it "not wanting to take off", The Megacycle X12 is a good streetable cam. with a bit more torque at top end than the SRM cam.


From imagination, progress is formed.


... But not always. Most of its just tosh! beerchug
#687803 - 03/12/17 3:29 pm Re: 1970 Thunderbolt [Re: Allan Gill]  
Joined: Nov 2011
Posts: 77
GreenMonster Offline
BritBike Forum member
GreenMonster  Offline
BritBike Forum member

Joined: Nov 2011
Posts: 77
NH
Hello Allan:

I appreciate your feedback regarding the cam, I ran this cam years ago and loved it! I never an issue so why spend another $400.00? Actually it replaced a POS Megacycle cam whom I will never do business with ever again.

I do not know about the SRM X12 who makes the cam? or do they just have a stock cam magnafluxed, spray welded and ground to spec?

I will agree that the T-Bolt cannot breath well when pushed but truth be told, neither can a Lightening my 2000 Concours would eat both for lunch.

Feel free to move this post if you deem it necessary.

Thank You


Never Allow The Radical Views Of The Few To Infringe On The Constitutional Rights Of The Many
#688694 - 03/19/17 11:44 pm Re: 1970 Thunderbolt [Re: GreenMonster]  
Joined: May 2013
Posts: 4,232
Allan Gill Online sleepy
Allan Gill  Online Sleepy



Joined: May 2013
Posts: 4,232
Rotherham - S. Yorkshire
Which megacycle cam did you use?

The SRM is their own race cam, similar to the Johnson 380 (from memory) but unlike the johnson or megacycle cams, the SRM can use 1.25" (standard) or 1.125" follower radius, Johnson and megacycle spec 0.75" radius, if you didn't do this then you may have found your problem.

The X12 from Megacycle is a road race/street cam. With standard exhaust it makes a lovely street cam with good top end. However I spent the weekend making a new exhaust to marry up with a Dunstall (genuine) muffler 2-1 the silencer is a lot further forward and boy has it got some bark. Its first time back with the rear sets and my over worked memory had me going in 4th instead of first and it still pulled away, quite easily. in first it was hard to keep the front end down! Certainly a different beast.


From imagination, progress is formed.


... But not always. Most of its just tosh! beerchug

Moderated by  Allan Gill 


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