Topic: Cam difference?

[ramerbikeshop]

I got a parts engine that the owner said had a different cam.  The stock one said R8. And the other one says R9.  What is the difference between an R8 and R9 cam?

[KRONUS0100]

production series numbers.   the r9 is newer than the r8

[ramerbikeshop]

There is no difference in duration or lift?

[754]

Most stock cams are relatively close, the F models on 750 are hotter, and the early K .
 However the numbers stamped or marked on them usually have very little meaning. If its out check the lift with a mic or calipers.. If you have 2 cams ..compare them visually.

 Even a drop in hotter cam, or a late F cam are visibly different, than the mid years K cams..

Check valve lash first, just in case.. If not stock WRITE it down..

[ramerbikeshop]

I will check them out again and measure them. Thanks for the help

[Bodi]

The cast-in numbers indicate the particular wooden "dummy" cam used when making the foundry sand mold for a cam casting. There were a few of them, they made a lot of cams and wanted to prepare more than one mold at a time. The dummies are numbered so if one got damaged and the cam blanks cast from it were discovered to be defective, they could know which one to repair or toss out. This number has no direct relation to the cam's final profile. The numbers used changed during the production runs of each bike as some got damaged and retired. Possibly some number changes are related to changes in the cam grind that wouldn't work with the old castings, I don't know either way about that - maybe there is some production point where the cam casting numbers suddenly changed with the "old" ones disappearing.

[ramerbikeshop]

I checked the measurements and they are the same on the R8 and R9 cam. My next question is how hot a cam can I run with a stock bottom end?

[754]

Quite a few of us have ran hot street cams with 836 cc on stock lower ends. Not really recommended, but happens and they can last pretty long.

 More important,how do you want to ride it, and what else are you planning to do to it..

[Jerry Rxman Griffin aka MuthaF'er]

I wouldn't worry too much about how hot a cam vs the bottom end. As for the bottom end you probably need to be concerned more about displacement. We'd generally recommend stronger rods above 836 if you're gonna run tha dog #$%* outta it especially if you go with other HP increasing goodies. You can over-cam the rest of the stock engine though and it wouldn't perform well or be uncivilized for a daily rider.

R8 and R9 really don't mean squat when it comes to grinds. All you can do is measure the lobe heights and eye-ball the profile/duration. One looks bigger/better/badder thow that sum#$%* in and use some stronger valve springs so you don't float a lifter and destroy the engine.

[ramerbikeshop]

I would like to use the stock displacement and only change the cam. I am not looking to have a drag bike or a race bike but would like to have good throttle response and a little more pep than a box stock 750 that's why I was thinking cam. My worry was if I change the cam would I run into floating a valve by having a higher lift or a longer duration using stock pistons.

[754]

Springs will fix that..

 However , your 4-8 K powerband motor that. You now have, may turn into a 6500-10,500 powerband motor..

[Jerry Rxman Griffin aka MuthaF'er]

Springs will help prevent valve float but I don't expect valve float to happen within the redline, only north of the redline like on a missed shift at WFO whether a stock cam or a big cam. More likely on a big cam with bigger lobe profiles. Anyway, it's good insurance and better performance.

[ramerbikeshop]

I wouldn't mind having a higher powerband. I already have a header and jetted carbs and am planning to put an electronic ignition in as well.  Would a hot street cam perform well with my adjustments? If so what for pressure valve springs should I look at?

[Jerry Rxman Griffin aka MuthaF'er]

Sure, a hot street cam would go with your ideas. Sometimes a 'lesser' hot street cam may be preferential unless you want to twist it to 10,000 often. You'd be looking a mid-range power in that scenario which isn't a bad thing but I personally like the sound and feel of HP at 10,000rpm. Most of the stronger cams go in the 7,000 to 10,000 band but the real benefits of this requires some good $$$ head work. Not saying though that you have to have head work as that's generally the next step up in performance and $$$. 

I haven't shopped for springs in a while so I'm not current on them. I had MRieck do my last head and he used Kibblewhite (KPM) parts. APE has them too. These are 2 of the most reputable brands going but there are others too. CycleX has hipo stuff too then there is Dynoman. I have dealt with all of them. 

[ramerbikeshop]

Could you give me some names of performance shops to contact in looking for cams?

[crazypj]

Unless you actually intend to use more rpm than stock a hotter cam is a waste of time and money.
A better ignition system would be first priority. If you find you out the other side of red zone a lot, then you would need a cam (or more modern bike  )
If your going to putt around and rarely get over 6k you will not like the way it runs

[ramerbikeshop]

I found a good street cam that I can still use with my stock valve train.  It is a web, high performance street cam, it has 10 degrees more duration than stock. I think that will go well with my other modifications.

[Jerry Rxman Griffin aka MuthaF'er]

Probably, but which Web cam? They do 'stock-like' cams too. Advertising sells #$%*. experience builds #$%*.... Model number? 63A ? Should work with MOSTLY stock. I wouldn't go less but I wouldn't do the B with what you are looking at. The A is more mid and the B is more top rpm. Regardless, install better springs. I missed a 1 - 2 shift and floated a valve into my piston. Nuclear! 

Agreed with PJ, if you are going to play then upgrade your ignition too at some point in this process. It'll get additive with equals expensive. Electronic ignition with hotter coils which also relieves you of the stock worn out wires and caps. Set 'em and forget 'em! WTH, you're getting into $$ territory anyway...

[Don R]

 ARP, dynoman, Megacycle, Cycle X. There was a thread a while back in the hi perf section that had quite a bit of information. Search (favorite cam)

 Me too on the springs. I put a stock F2 honda cam in my 836, the second week I missed a shift and at the next stoplight pop ummmm pop ummmm pop umm. Tagged the #4 exhaust valve. Now I have a bigger cam, ported head and ARP springs/retainers. I've only got a few blocks on it so far.

[ramerbikeshop]

The web cam is a 41a which is 275 degrees duration and the site says stock springs are ok.  But notes to check all clearances ahead of time. I have looked at pamco ignitions and will have an electronic ignition before the bike has it's first start up.

[Jerry Rxman Griffin aka MuthaF'er]

Yeah, you CAN run stock springs but....... it's good insurance. I blew mine with a stock 6000 mile 75 750F engine when I missed the shift. Stronger springs would have PROBABLY prevented that COSTLY mistake. All depends on how you ride!!

[ramerbikeshop]

I looked at getting springs from web too, they Are high po dual springs for k models. I'll go with those

[crazypj]

Honda did various modifications and tweaks over production life of motor. Sometimes cam would have few degrees different opening/closing points, lobe separation or similar.
Carb's were generally changed at the same time or sometimes the slow/pilot jet size would change
There may or may not be a service bulletin notifying dealers of cam change but generally it was just the jet changes or carb changes (sometimes somewhere on the page it would say why, - better low speed running and changed cam timing, etc)
You would probably have to degree hundreds of 750 cams to work out what changed plus of course, there are the production variations
Anyway, purpose of post 
You may find variations of stock springs, original inner's are sometimes stiffer than aftermarket outer's (and same with outer's but that's less likely)
Stock springs fro various years changed seat pressure
If you are not sure what you've got and don't have anything for comparison, it would be best to get either stock springs specific to the year before cam was first made or, aftermarket heavy duty (simplest thing to do)
Hopefully, this may explain to anyone else reading it why you need to change valve springs when you fit a 'hotter' cam