Can anyone double-check/recommend my rejetting?

[G.S.Joe]

My bike is coming together, and I'm having difficulty getting it to not cut-out. The previous owner started to cafe it but didn't finish. Carbs look stock (1978 GS750), and have 102 mains, slow is a 15. From what I'm reading with open manifold and pod filters I should be running 3 sizes bigger, so a 109.5 main, and a 17.5 slow jet.

First, before I buy anything, can anyone confirm I'm going in the right direction? And, similarly, can anybody recommend a brand/seller?

As always, thanks.

 

[tom203]

I'm not real familar with the VM carbs, but yes, with pods, you need to go up on mains; you probably have seen this chart from Basscliff

http://members.dslextreme.com/users/bikecliff/images/carbspec_float_height.html#A01

Hang in there, someone knowledgeable will chime in

 

[rustybronco]

What do you mean by open manifold? No exhaust system whatsoever?

 

[allojohn]

I run a 78 750 with K&N pods and V&H pipe. 15 pilot and 117.5 mains.

 

[Guest]

Eric sent me this to help you out;

Just tell him to buy the 107.5 and 110 main jets from Z1 Enterprises and keep the stock 15 pilot jet in them.
Try the 107.5's first and adjust the fuel and air screws.
That should be all that he really needs to do besides ride it.

Edit: this is assuming you have stock exhaust.
Eric

He seems to know pods, that's about all he uses on his bikes.

 

[G.S.Joe]

What do you mean by open manifold? No exhaust system whatsoever?

I'm afraid I'm new to bikes and I used the term in an automotive sense. I have what many might call "headers", but they're stock, so I refer to them as manifolds. Is that incorrect? I always thought headers = aftermarket manifolds.

 

[G.S.Joe]

Eric sent me this to help you out;

Just tell him to buy the 107.5 and 110 main jets from Z1 Enterprises and keep the stock 15 pilot jet in them.
Try the 107.5's first and adjust the fuel and air screws.
That should be all that he really needs to do besides ride it.

Edit: this is assuming you have stock exhaust.
Eric

He seems to know pods, that's about all he uses on his bikes.

Thanks! I do have open headers or manifold, or whatever you want to call it. No mufflers.

 

[tom203]

I'm afraid I'm new to bikes and I used the term in an automotive sense. I have what many might call "headers", but they're stock, so I refer to them as manifolds. Is that incorrect? I always thought headers = aftermarket manifolds.

The bike left factory with "headers" - something like you might put on a car that had a cheapo exhaust "manifold". But do you have mufflers attached to these headers? OOPs, I see your new post- no mufflers! This likely changes the jetting requirements- do you live in a noisy neighborhood?

 

[rustybronco]

First, do yourself and others a favor, find some mufflers to put on that thing then work on jetting it properly.

 

[G.S.Joe]

The bike left factory with "headers" - something like you might put on a car that had a cheapo exhaust "manifold". But do you have mufflers attached to these headers? OOPs, I see your new post- no mufflers! This likely changes the jetting requirements- do you live in a noisy neighborhood?

I live in a place where I have satellite internet because nobody will run cable out to me, and my town's post office does not deliver my mail.

Unless the bears learn how to dial phone I'm not worried about anybody calling the cops.

 

[G.S.Joe]

First, do yourself and others a favor, find some mufflers to put on that thing then work on jetting it properly.

I've been on the lookout for a decent price, but this is a budget-build unfortunately. I'm fine spending X dollars on the necessary stuff like gaskets/rebuild kits and anything else rubber. I was hoping to get away from spending $150+ for a used, rusted exhaust on a $500 bike unless I needed to. Is the scavenging thrown off that much? As I said, I'm still learning and have seen others with "good" running bikes with open headers as long as they're tuned properly, but maybe they're not running so "good" after all... :-k

 

[G.S.Joe]

I run a 78 750 with K&N pods and V&H pipe. 15 pilot and 117.5 mains.

Those sound like huge mains. Does it run well for you? Plugs look good?

 

[rustybronco]

Those sound like huge mains. Does it run well for you? Plugs look good?

There not even close to being huge. The last Gs750 I jetted with pods and a 4-into 1 took 125.0's.

 

[tom203]

I live in a place where I have satellite internet because nobody will run cable out to me, and my town's post office does not deliver my mail.

Unless the bears learn how to dial phone I'm not worried about anybody calling the cops.

"satellite internet" both ways? I need to dump my cable service -what a ripoff!
Even in the boonies of Western Mass, you probably got harley riders and dealers to pamper them. Check CL for harley takeoff mufflers -the stock ones often get orphaned quick to enhance the ride. Typically, in my area, a set goes for about $50.

 

[tom203]

Muffler sets are getting cheaper all the time - why go deaf on your way to post office?

http://maine.craigslist.org/mcy/3771748912.html

 

[G.S.Joe]

"satellite internet" both ways? I need to dump my cable service -what a ripoff!
Even in the boonies of Western Mass, you probably got harley riders and dealers to pamper them. Check CL for harley takeoff mufflers -the stock ones often get orphaned quick to enhance the ride. Typically, in my area, a set goes for about $50.

I'm not sure if you're serious, but satellite internet is horrible. I hit my daily cap after ~30 minutes of streaming, it cuts out when it rains, the satellite goes out for no reason, it's $70/month...

Anyway, thanks for the Harley muffler idea. I didn't realize they were so cheap. I'd still need to get 4 or buy a 4-2 setup with 2 mufflers, but if I can get them at $25 each and somehow mount them without any welding I'm happy.

 

[allojohn]

Those sound like huge mains. Does it run well for you? Plugs look good?

Runs great, and as RustyB says 117.5 isn't overly large.