First some specifications;
lifts are gross valve lift off of the seat. Rocker ratios were 1.347:1 for the TR1;
durations are taken from the point that the valve exceeds 1mm lift off of its seat until the point at which it falls
below that. The only TR1 parts books I have are for the French market '81 and the Scandinavian market '82. Both specify 4X7 cams;
I presume that all TR1 variants also had these cams as Yamaha had very lazy engineers.
- Gen 1
- Valve Lift(mm):
- Lobe Centers:
- Intake Open
- 15° BTDC
- 32.5° BTDC
- 23° BTDC
- 43° BTDC
- Exhaust Open
- 51° BBDC
- 64.5° BBDC
- 47° ABDC
- 77° BBDC
BT-C01: These cams have 12.5mm lift
and 270 degrees duration. Note: if you use Yamaha factory service manuals to find cam specs, you will find truly astonishing road-race-sounding durations;
reputable after-market cam vendors quote duration beginning and ending when the valve is 1mm off of its seat;
Yamaha appears to count duration as including any time the valves experience any lift at all, including the longish "acceleration" ramps.
The stock springs coil-bind at 11.2mm lift and float at 8000rpm.
I've run a similar combination up to 8900: where the rev limiter closed things down.
These are not a drop-in. You must at least notch the pistons for valve clearance, unless you are running after-market pistons like our 1004cc or 1065cc kits.
These are road race cams (although I had no problem running a set on the street). They are made to rev.
To fully benefit from these cams, you should run 10:1 or higher pistons, a free-flowing exhaust, and carbs with accelerator pumps.
It wouldn't hurt to open the ports a little. A multi-angle valve job would help.
Keep in mind that raising compression means more stress on your starter and related parts;
you should stake the ring (sun) gear inside the starter motor to the housing so it does not just spin without turning the engine.
BT-C05: some cams that don't require spring kits.
At last: more power without having to pull the engine. These cams can be swapped-in in your driveway in under an hour. They have 11mm lift and 264 degrees duration.
A real punch in the mid-range (think passing power) and finally the ability to rev a little.
These cams are meant to be used in an otherwise stock engine -- although they would benefit from pipes and carbs (and compression).
They push the stock springs pretty hard, so try to stay under eight grand.
Nothing NEEDS to be changed, but you may want to put some washers under your jet needles.
A good cam if you're looking to make a café racer. Pipes a must, carbs recommended.
For the bigger bikes, look for a greater willingness to rev -- you'll think your twin has "gone Italian."
As with any longish duration cam, a little of the bottom goes away, but gobs of power are to be found from thirty five hundred on up past red line.
These cams have over a quarter inch more lift than any stock XV. See our rocker page.
If you have the hole-in-the-pad unhardened rockers keep plenty of fresh oil in your motor. Change it frequently. Run an oil that contains zinc.
Your beast will finally take the deep breaths that a big twin with big valves should.
BT-C06: These are too much cam for any stock displacement XV.
These are our cam of choice for the TR1 with the 1065cc kit. These are based on flat-track profiles. They spin up faster than the BT-C01.
The lift is enormous and the duration long in the extreme. They don't idle well with constant velocity carbs.
Even with flat-slides, a stable idle will be between 1200 and 1500RPM. The lift helps give back some of the low-end that
the duration takes away. NOT recommended for commuter bikes. Meant to run with a minimum max rev of 10,000RPM.
It is not recommended to exceed ten five, as I believe that the tensioners are designed (not by intention) to grenade somewhere between
eleven and eleven five.
Also note well, cam prices are exchange or out-right. Cores are costly.
The BT-C01 and BT-C06 cams require spring kits, which requires pulling the heads -- on a Gen I, this means dropping the engine.
A good time to install a big bore kit
The combination of pistons and cams will have you looking for ways around the rev limiter cut-off. Look at Ignitech
(we'll add these, but not soon), or exercise some patience while we sort out our cam-driven single spark ignition.
There are some mighty gimmicky ("three sparks per ignition event") alternatives out there. They are pretty tidy,
but to buy everything needed for full tuability could easily run you a thousand - three times as much as the Ignitech.
Also, keep in mind that the cams have very little "flywheel" effect - they tend to move in-and-out and they self-retard under load - but not on a dyno!
Check out this page
Note the prices below now obtain. I am often out of cores and there are suddenly few to be gotten.
Titanium jumped very high. Use the contact button on the front page to tell me what you want and I'll send you an invoice.
Right now, if you want cams outright, I'll have to buy good cams and weld and grind them.
The cam and titanium spring kit combo would go for $1050.
If you sent me your cams first and I found them useable, I'd invoice you $850.
Cams outright are now $735; send yours first, $535.
Titanium topped spring kits are now $325.
Queries from the contact button often proceed to dialogues that end in steep package discounts
$1050 BT-C01 or BT-C06 Road Race Profile Camshafts (no exchange needed) with Titanium Spring Kit.
Note that if you get the kit above, you are already getting the spring kit listed below.
Note that the reciprocating parts (less valves) in a stock XV are 110 to 116 grams -- this is springs, retainers, and keepers.
The same parts in the following kit weigh 79.3 grams. Less reciprrocating weight equals faster spin-up; less float likely.
$325 High Performance Valve Springs with Titanium Retainers - Good to 15mm Valve Lift
$275 High Performance Valve Springs with Chrome Moly Retainers - Good to 15mm Valve Lift
As durable as the titanium, but without the glamour of being able to say that your bike contains titaniun.
Some thoughts on Springs.