real world effect of modifications to motor

[Deano]

It seems most of us are OK with the scramblers power down low, but a little dissapointed at highway speeds.
Can anyone tell me how the modifications they made to their motor effect the bike at higher speeds. e.g. if thunderbike cams are fitted, does it noticably pick up speed for passing etc, compared to stock?

 

[FoothillRyder]

I've not taken the time, money or trouble to change camshafts or install a big-bore kit or any of those other expensive mods. On my Thruxton I found that simply letting the engine breathe by changing the exhaust, opening up the intake, and rejetting to account for those changes transformed the engine to the tune of a 12hp gain and the ability to slam into the rev limiter in any gear where it would run out of breath, especially in 4th and 5th gear, when stock.

On the Scrambler I've found essentially the same gain, although I've not put it on a dyno. Open up the exhaust and intake, rejet, and the bike feels a LOT stronger at the top of the rev range. I have no issues with the power now.

 

[Aussiebikerdave]

Deano, the Hinkley twin responds very well to engine mods for more power. As Fotthillrider says, allowing it to breath with better pipes and an airbox removal kit will help heaps but there is a swag of steps after this that you can take all the way to about 90 RWHP... depending on how much you want to spend. Here is the list.

Wiseco 904cc big bore kit.
Cams, Thunderbike or TPUSA 813 grind.
Port and polish cylinder head.
Bigger valves eg, 2mm o/s for inlet and exhaust.
Fit 39mm carbies or if EFI model, have the throttle bodies bored to 39mm and flowed by Triumph Twin Power, Bournmouth, UK.
Lighten flywheel by 1.2kg and rebalance.
Fit TPUSA 994cc billet barrel instead of Wiseco 904 BBK.

Doing all of this will net about 90hp still with great usability and reliability as I have done with my bike but if you didn't want to go the whole hog just fit the performance pipe, airbox removal kit and a performance cam for about 65RWHP as opposed to about 46 RWHP for a bone stock Scrambler. I suggest these three things because they are all quite easy and quick to fit so assuming you get the shop to do the work, it wont cost an arm and a leg for labour.

 

[strokerlmt]

Letting the engine breath is something I believe in. I have 1.5 inch to 1.75 inch headers to 2 inch throat on a dominator muffler. No air box re jet and it makes a big difference. Having said that when I ride a stock Bonne / Thrux it feels like a scooter compared to the engine I have 988cc 813 cams fcr 39's. Once you have the 90+ hp it is hard going back.
LMT

 

[Twodogs]

Deano, the Hinkley twin responds very well to engine mods for more power. As Fotthillrider says, allowing it to breath with better pipes and an airbox removal kit will help heaps but there is a swag of steps after this that you can take all the way to about 90 RWHP... depending on how much you want to spend. Here is the list.

Wiseco 904cc big bore kit.
Cams, Thunderbike or TPUSA 813 grind.
Port and polish cylinder head.
Bigger valves eg, 2mm o/s for inlet and exhaust.
Fit 39mm carbies or if EFI model, have the throttle bodies bored to 39mm and flowed by Triumph Twin Power, Bournmouth, UK.
Lighten flywheel by 1.2kg and rebalance.
Fit TPUSA 994cc billet barrel instead of Wiseco 904 BBK.

Doing all of this will net about 90hp still with great usability and reliability as I have done with my bike but if you didn't want to go the whole hog just fit the performance pipe, airbox removal kit and a performance cam for about 65RWHP as opposed to about 46 RWHP for a bone stock Scrambler. I suggest these three things because they are all quite easy and quick to fit so assuming you get the shop to do the work, it wont cost an arm and a leg for labour.

Hey Aussiebikerdave, I am down in Ipswich and would like to know did you import your parts or do you know of a good supplier of after market bits and a good engine machinist for the head work etc in SEQ? I would love to go all out with my Thruxton but am getting a little peeved with having to keep buying bits from the States and the UK because if there is any problems it becomes a pain to try and get things sorted. I am actually stuck with a Barnett clutch at the moment because it performs hopelessly but the supplier in the States has had no complaints before and Barnett have no suggestions. Be a hell of a lot easier to deal with somebody I can look into the eye. Cheers Twodogs .....(not twoheads)