Topic: Honest opinion needed

[88BuckMeister]

I'm new to this and I feel like I'm somewhat over my head. I'm in the process of a 650-550 cam swap with a 591cc 61mm piston kit. I shaved material out of the head to get the lobes to clear. Now I apparently have to check to make sure the lobes don't contact the rocker arms and do a mock assembly using clay to check valve clearances. I feel like if I am going to follow though with this mod, now would be the time to do it with the engine out of the bike. I do have a new stock grind cam for it too...I keep asking myself...should I just put the damn thing together with the stock cam? Will I ever follow through with the 650 cam upgrade down the line?

Thus far I've purchased the 650 cam, the new tach drive, racing valve springs from Dynoman, I've already got the 591cc big bore kit installed, I bought a 16 tooth front sprocket, and that's where I'm at.

What is your guys' advise. Will the power boost be THAT MUCH MORE that you day "dude take your time, this mod is worth it", or is it that "your 61mm big bore piston kit is sufficient, just put the new stock grind cam in. It's not that big a difference in power". I've never ridden this bike or any 550 for that matter before so it's not like I even have anything to compare it to anyways. Thoughts? Somebody sway me. It'll be a LOT less of a headache to use the new stock grind cam. But if the 650 cam mod is worth the headache, let me know and I'll follow through. Just reading a lot of horror stories from people that "missed something" in the process of this mod

[scottly]

Just install the stock cam for now and save yourself the anguish.

[newday777]

If you are wishy washy in your abilities,  get hold of Kurt Jordan out in San Diego. He has built many of these 650 conversions and knows them well, he is in high demand because of his expertise doing race motors and was a racer too with these.

[seanbarney41]

If you can find similar dimensioned light weight springs, at say the hardware store, there is a better way to check piston to valve clearance.  What piston kit did you use?  Wiseco's?  Gonna be a significant bump in compression, which is gonna improve performance more significantly than just an increase in displacement, but may be detonation prone with stock cam.  If you used chinese flat tops, not much compression gain, and not much performance gain either.  However I don't think the 650 cam is a huge difference from the 550...especially compared to a true performance or race grind...the 650 cam in a 550 was always more of just "well it's cheap and easy and it's slightly better so if one is available, might as well use it" type of thing...not to say that many have not been happy with it.

[Mark1976]

   So, regardless of the method you choose to determine piston to valve clearance's, finding out what the numbers are is what's important and at the worst your out the cost of a head gasket, maybe even a base gasket (chicken scratch). We'll be able find out what a proper number is as you progress. When in doubt go back to your piston mfgr and see what information they may have to offer. It takes a little effort and time but its what you have to do to assure its not going to turn into a pile of useless metal and frustration.
   If not, just install a stock 550 cam and be done with it. Of course you'll never really know what the potential the larger bore has to offer as well as the knowledge gained from properly following thru.
   Spend a little more time researching the methods of determining valve to piston clearance,  its not difficult, its a learning experience. Your in Illinois, its not like you can ride it tomorrow. When you have a engine build of this nature various parts (cam), various suppliers (pistons, gaskets) you don't just throw it together. Well, you can, but you sure as hell shouldn't. It'll take some well invested time, but won't be a waste of time either.

[88BuckMeister]

   So, regardless of the method you choose to determine piston to valve clearance's, finding out what the numbers are is what's important and at the worst your out the cost of a head gasket, maybe even a base gasket (chicken scratch). We'll be able find out what a proper number is as you progress. When in doubt go back to your piston mfgr and see what information they may have to offer. It takes a little effort and time but its what you have to do to assure its not going to turn into a pile of useless metal and frustration.
   If not, just install a stock 550 cam and be done with it. Of course you'll never really know what the potential the larger bore has to offer as well as the knowledge gained from properly following thru.
   Spend a little more time researching the methods of determining valve to piston clearance,  its not difficult, its a learning experience. Your in Illinois, its not like you can ride it tomorrow. When you have a engine build of this nature various parts (cam), various suppliers (pistons, gaskets) you don't just throw it together. Well, you can, but you sure as hell shouldn't. It'll take some well invested time, but won't be a waste of time either.

You mentioned base gaskets lol now I'll be the first to tell you you're the one who has inspired me to see this theiugh, and as you said, with time and patience I've been pleased with the results. Ugh but that base gasket...everything on this motor is high end, the base gasket looked cheap. Of was from 4-into-1. My old man says look it's not a head gasket, it'll work fine. Will it? Do I need a high end base gasket? Ugh that means I'd have to take the cylinders back off. Those were a nightmare with bent rings and re-bores galore. I think it'll do the job

[calj737]

The base gasket is not critical. Keep the one you have installed.

[Mark1976]

The base gasket is not critical. Keep the one you have installed.

+1

[grcamna2]

I have no actual experience with installing and running a CB650 camshaft in the 550 engine;with that in mind,I would still 'go for it' and install the 650 camshaft. I say this because it's what I would personally choose to do,for what it's worth.