1100g d port head on 1000

[Buffalo Bill]

Your 1100G is an 8 valve, yes ? My favourite lobe centers for the 8V's are 107/108. Many years back I did an 1100G to 104/106 to see what it was like. As it turned out, after I'd sorted the carburation it was a rocket. The owner went looking for GSXR1100's to challenge to top gear roll-on's. He won a lot of beer...

Thanks! Some true anecdotal experience goes a long way. Won't have to spend much money to degree the cams. New Web Cams wow, quite pricey!

 

[GregT]

Thanks! Some true anecdotal experience goes a long way. Won't have to spend much money to degree the cams. New Web Cams wow, quite pricey!

Last time I bought Webs was a few years back when your dollar was low. Talking to the sales staff they were surprised at how many overseas orders they were getting at the time. I told them the facts of life re buying from the US from an overseas point of view....
Generally they are too expensive. I can get cams ground locally for less - and to my specs.

 

[srsupertrap]

I have done the D-Port head with a Wiseco 1100 installed in bored 1100G cylinders, Andrews Cam, RS34 Smoothbores. Good street bike with more torque but 1100G cylinders weigh significantly more than 1000/1085 bored cylinders

https://www.thegsresources.com/_for...-amp-Mikuni-RS34&highlight=GS1100+d+port+head

 

[limeex2]

I am in the process of having a 1100g top end set done on a 78 1000. The 78 needed all top end gaskets, a carb overhaul and an ignition. For not much more (it cost me $150) I got a complete top end, ignition and carbs. Its a street bike and wont be ridden like it was stolen. When its done it may not be faster, but should have roll better on's, and with cv carbs, easier for the tuner. So with stock cams, did we like cam timing at 107/108 or 104/106?

 

[GregT]

I am in the process of having a 1100g top end set done on a 78 1000. The 78 needed all top end gaskets, a carb overhaul and an ignition. For not much more (it cost me $150) I got a complete top end, ignition and carbs. Its a street bike and wont be ridden like it was stolen. When its done it may not be faster, but should have roll better on's, and with cv carbs, easier for the tuner. So with stock cams, did we like cam timing at 107/108 or 104/106?

The port velocity will be significantly lower than optimum. I'd try it at 107/109 for a start. If you slot the sprockets it's easy enough to change the timing in the bike - and you certainly won't have any valve to piston problems.

 

[limeex2]

Educate me. If compression ratio is raised to stock levels w/cyl machining and entire top end inc carbs are stock, what is the cause of lower port velocity?

 

[thebrandonbeezy]

Bigger ports the flow better but on the smaller displacement theres not enough engine to make a great use of the head

 

[GregT]

Bigger ports the flow better but on the smaller displacement theres not enough engine to make a great use of the head

Correct. When using carburettors, there's an ideal port velocity to aim for - at least on the street. Ports which are too large in relation to the engine displacement suffer from too low a velocity and can be very hard to tune carbs for...

Of recent years, as injection has become common, port sizes have gone back up. If you don't have to depend on the port velocity to atomise fuel in a carb, but instead it's atomised in a pressure nozzle, the sky's the limit on port size.

 

[Chuck78]

Educate me. If compression ratio is raised to stock levels w/cyl machining and entire top end inc carbs are stock, what is the cause of lower port velocity?

Larger ports = more space to fill, therefore there is a lag in throttle response as the slower filling big ports ger filled up when opening the throttle

 

[limeex2]

Larger ports = more space to fill, therefore there is a lag in throttle response as the slower filling big ports ger filled up when opening the throttle

Thank you, this part I now understand. Let me re-word it.

If I raise the lost compression to std levels, use 1100g head,cams and carbs, would it essentially be a smaller bore 1100g? I like CV carbs over the slide type that came on the 78 GS1000 and dont want/need a big bore kit.