Yamaha Genuine Racing Cam

[charge]

Yesterday I tried out Yamaha Genuine racing camshaft. It cost about USD45.

After a lot of tunings done (by mechanic), including rejetting stock Mikuni carb, I went out for a test ride. Darn, I am quite disappointed by the power curve.

The low rpm torque is screwed up, worse than stock a lot. mid rpm also screwed up, but at high rpm, the power comes suddenly.

The mechanic said my carb is too small for this camshaft. When I full throttle, the engine response is damn slow, and when it reached mid rpm, it jerk a lil before moving to high rpm.

Darn... feel like riding a bike with big 'turbo lag'


Erm... from technical perspective, the lobe angle is smaller but the lobe looks more 'round' compared to stock camshaft. My guess is, this camshaft aims for peak power by reducing the valve overlapping?


I gotta bear with this sucky power curve until I got enough cash to try another cam setting.

 

[haen]

have u tried different valve clearance.. like 20 IN - 15 out maybe.. i got this kind of experience too using 'fat' cams.. trying lots of valve settings 10- 15, 10-10, 10-20.. til i got that strange number.. 20 -15.. but it makes the engine ticking sound due to low valve lift setting..

 

[charge]

have u tried different valve clearance.. like 20 IN - 15 out maybe.. i got this kind of experience too using 'fat' cams.. trying lots of valve settings 10- 15, 10-10, 10-20.. til i got that strange number.. 20 -15.. but it makes the engine ticking sound due to low valve lift setting..

bro haen, thanks for your advice.

Just wondering, the mechanic was adjusting some kind of chain, is that valve clearance adjustment?

Anyway, there is a mistake in my 1st post. The lobe separation is wider compared to stock while the lobe is slightly fatter. I think this cam decreased the intake-exhaust overlapping and robs a lot of my low end torque.

I am wondering, does bigger carb helps to solve the jerky problem?

 

[phl6684]

yes bro..if u have bigger carb..it will "masok trus".hehehee..coz the carb intake is big enough 2 make the a/f mix to enter the combustion chamber..rite guys??if im wrong plz correct me..

 

[haen]

i think ur cam is a drag/racing cam type, which made purely for hi rpm.. thats why the LSA is wider but fatter.. fat cam means longer duration.. i guess thats the 330 deg cam..

 

[charge]

ohhh.... how do u measure the 330 deg?
After some warming up, the powerband seems smoother, but still got a power dip when I suddenly full throttle.

Currently my carb pilot air screw setting caused the idling rpm high. I requested to change pilot jet to a bigger size one, but the mechanic said mainjet alone is enough. Do you think I should change the jetting or change the whole carb to bigger one?

 

[haen]

jetting change wont give much effect if the profile of the cam already set to some area of powerband.. i already tried many combination of jetting.. the needle clip positioning almost work.. but it turns out that its the profile of the stock needle doesn't suite the cam profile.. thats the source of the power dip at middle rpm range.. especially when accelerating.. but try valve clearance settings first.. might help..

 

[lc-motospeed]

@charge
the 330 degrees is calculated at the lobe of the cam

 

[joel]

Hi All,
I've gott a cam for my R15 through TDR.
It has a very high duration over stock. However the lift is same.
Installled and the power was dead till 7000rpm. And then shoots. Throttle response was nil.. Felt like the engine will stall.
i compared the lobes with he stock cam and the duration is only higher.
I've also upped the compression on my engine. Currently running 12.3:1 comp ratio already
I have deeper valve pockets and works
the r15 runs FI and we cant richen the mixture too.
Any suggestions. The cam is lying pretty useless, wanna make it run.

 

[goff_d_p35]

yeah,mod the engine to work for a carb, get rid of the ECU and get the Rextor CDI. then you can get more performance out of the ECU designed engine.

 

[charge]

thanks for your explanation lc-motospeed

bro haen, I've tried a few mechanics at my place, all of them refuse to set the valve clearance for me. They said it is ok ady, its all the carburetion problem... sigh.. I guess they dunno how to set thou.

btw, one of my fren helped me to polish the outer part of the carburetor intake port, make it like a funnel. Then we also try to reset the TPS (turning downwards) and reset the idle air-fuel. The throttle response becomes much better, but there is still a power dip at mid range rpm. Phew... that takes us about 6 hours man @_@
anyway, we'll try out your tips on needle jet this weekend. May I know what brand is good? How 'fat' do you think the needle should be? Thanks man.

Joel, my racing cam is same like you, after abt 7000rpm the power suddenly comes. It is very bad for normal road riding and hill run, but high speed corner really rox!! I'll revert back to stock cam someday, now I wanna get some experience on carb settings and valve clearance, never tried before in my life, lol. Now, me and my LC lost virginity together, we had our first time

 

[joel]

I have an idea and its something which u guys can try.
To make this cam work, u can set the cam timing about 5 deg retarded. You will gain most of the lost low end power. The power delivery after 7k rpm will not be as strong as earlier, but it will be a good street set-up.
Even with the stock cam, u can have 3 settings for performance.
5 deg retarded cam position, can give u loads of low end torque. Normal cam setting will give u stock bike feel and 10 deg advance on the cam will give u very bad low end and awesome high end pulse. The band will be really string after 6k rpm. Will make u feel ur running a works cam already.

 

[charge]

I see no cam pulley
Gosh, how do u advance / retard the cam?

 

[joel]

Just jump the notches on the cam chain. Just run one notch front or back. Would make it advance or retard.

 

[haen]

it's simple.. look at the cam sprocket.. divide 360 by sprocket notch.. u got degrees per sprocket notch...

 

[joel]

does anyone here know the exact count of the cam wheel? I've not counted but only measured the retard and advance on an angle finder.

 

[Arul365]

anybody know how to setting the T135 LC because i use the CDI racing BRT...

 

[charge]

thanks alot joel and haen.

hey Joel, when I open the cam sprocket one day, will let you know the teeth count. I am currently broke after changing camshaft and Mikuni 28mm carb. I have no skill to open the bike all by myself, need to pay workshop to help me along, hehehe.

After using 28mm carb, the low end torque increased a lot, almost like my stock LC. Mid high rpm onwards (i guess around 7000rpm onwards), power keep coming until 11krpm. After that the power is flat out and dip near the maximum rpm (CDI set at 12.5krpm max).

Wow, I love the high-revving feel. The biggest drawback is cold start. This morning I use the electric starter until running out of battery, and Mikuni 28mm choke cannot attach to the stock choke cable, damn it.....

 

[joel]

Sure, please let me know once u open the head the next time.
Its pretty easy to work on the engine.

 

[inspire]

hi charge,
nice to know you've tried n tested the yam race cam. I'm having similar problems wif this newly installed rideit lo-cam. It really affected the low-end torque and mid-range pull compared to the standard. But it'll pull whenever the speedo is at 100kmh (m'sia std).
Now, advancing 1 tooth up or down has made some clunking noise from inside, probably valves knocking on the piston dome. To retard 5 deg would definately need an adjustable one. I'm hoping it's available for our kind.
Mind you this setup was done using stock carbs and oversized manifold mated to stock mufflers (wif catalyzer).
Thanks to a fren o mine, I've got a kangaroo exhaust system (similar to AHM, but deeper bang) installed and improved a lot. Pilot screw is 2 1/4 turns out. Downside is that you'll hear from a mile away.
Anyway hope to see you in penang end of month, KOM135 is visiting.