Head advice

Hey guys. As most of you know, my 650 is on the way to 810cc. My only stumbling block is the head. I know I can get a 750 head but I'm having trouble finding one, so I'm contemplating using my stock 650 head. I'll be running BS34's with pods, a yosh pipe and GPz camshafts. If I just do some port matching on the 650 head will she run ok? I dont trust myself to do any crazy porting. Something tells me I'll need bigger valves and ports though.

I dont see why that would be a bad combo at all. I believe that the 650 has a smaller conbustion chamber and will bump up compression a tad. Your engine combo is identical to mine except i am using a gpz head. What year 750 head is the one you need as it has provisions for the old style cam chain, 80? You will love this motor when it comes together.

Yeah it has to be a 1980, but I have heard rumours of other years having the provisions as well.

Thanks for the input, makes me feel better. I guess if it runs poorly I can just yank off the head and find a 750 one later.

I just saw pictures of a 650 head, that LarryC just finished. It is for a 700cc kit and will use 31mm carbs. It had D port intakes for mid range flow. This head flowed 120 cfm, thats more then a stock GPZ1100 head. Heres a picture, it has stock valves. Most guys wouldn't need that much flow, this bike will also be used at the track. Save your pennies and have Larry do you a street clean up. If Larry only gives you 80 or 90 cfm, thats equal to a stock GPZ1100 head. If you can ride, a head like that would be the real deal.

Are the valves still stock? I guess the advice I'm getting is "go for it", I'm glad.

T_Dub wrote:

Are the valves still stock? I guess the advice I'm getting is "go for it", I'm glad.

My advice is to use a 650 head, so you can use a smaller set of carbs. Why didn't Larry tell him to get a GPZ head? The answer -33's & 34's are to big and will kill the bottom end and mid range flow. Larry's a smart dude and has the equpt. to prove what he is saying. He tells people this over and over, somehow they don't listen and he stops talking. My advice, if your going to do it, do it right. Follow the guys that know how to make real horsepower, And yes the valves are stock and stock size........

hmm, I wouldn't mind trying smaller carbs, but arent they hard to come by? I went with BS34's because they're plentiful and they used to run on the GPz. I'm using GPz cams and I'm gonna be 3mm over the GPz bore, did Kawi put a carb on a bike that didn't need it?

I'me using 34's and my 810 runs great! Really screams up top, and can cruise around town at low rpm's all day.

T_Dub wrote:

hmm, I wouldn't mind trying smaller carbs, but arent they hard to come by? I went with BS34's because they're plentiful and they used to run on the GPz. I'm using GPz cams and I'm gonna be 3mm over the GPz bore, did Kawi put a carb on a bike that didn't need it?

Talk to Larry, ask him what he thinks of the small cams with something like 26mm or 28mm carbs. I would think one of his street clean ups, would be more then enough for a 810cc daily ridden street bike. Once you get a good head, you can change cams, etc. anytime you want. Larry is cool, he talks to those who will listen. I keep using the key word, listen. It doesn't hurt to ask him, he likes to help others. Check out his site.......

I was actually looking through old forum stuff on porting today and read a lot of the stuff he wrote. I shot him off an email earlier asking him about this, he definitely knows what he's talking about.

T_Dub wrote:

I was actually looking through old forum stuff on porting today and read a lot of the stuff he wrote. I shot him off an email earlier asking him about this, he definitely knows what he's talking about.

I find him to be a very nice guy. He likes his job and it has been his lifes work. He's not cheap, but without good porting your not going any place fast. I know everyone is on a budget these days, cut corners somewhere else and get a head that can flow. One of his heads can use small cams or big..............funny how I knew this, just one step ahead of you! hahaha

Yep, I'm sort of leaning that way now. Maybe I'll get him to port her out, that way I know I'm not going to have issues. He's actually not as expensive as some I've seen, for a Stage I port its $750 and that includes a valve job and a head resurface.