800 to 1000

[ChasF]

I want to take my 1981 R80G/S out to 1000cc. As far as I can see the alternatives are either a Siebenrock kit or standard R100 barrels with Richie Moore pistons. I want to stick with the standard smaller carbs and may fit the enduro cam as I'm looking for a good tourquey engine.

Is there any essential work required to the R80 heads to work with either of the above? I will change the rocker assemblies and probably the valves but as I haven't stripped it down yet I don't really know if the guides will need changing. AFAIK the engine has only done 30K miles.

I'm not going for out and out power just a good useable tourquey motor that will be a good compromise for road and trail use. Anyone any views on which would be the best set up to use?

 

[the civil one]

Scarilege .

If i could be so bold as to ask ,, apart from the obvious ,, why would you do this to a perfectly adequate motorcycle.
I have an R100GS Here , if you want it , i will trade you for your G/S .

 

[GADGET]

Not that your soliciting opinions..... but I'm with Civil..... keep it as it is

 

[sidestand]

I thought about doing the same with my R80GS
I was advised to keep it as it is - the 800 cc runs much more freely than the big bore conversion.

Lets face it, if you want handfuls of torque & power, an airhead isn't really the right starting point

 

[MikeO]

R80RTs always ran sweeter than R100RTs in my experience - the 800cc capacity just seemed to work better with that particular engine design - good luck with whatever you end up doing...

Mike

 

[Rob Farmer]

Moorespeed will bore out your 800cc barrels to 1000cc and re nikasil them (More than likely just do an exchange pair with yours) This will be a fraction of the cost of buying new barrels. You can then either buy another pair of heads from a later 800 and have them converted to 1000cc. The big advantage of this is you keep the smaller inlet ports and carbs which give more mid range and smoother running. If you keep the 800 bevel box you wont need an enduro gear. To be honest I never use first gear off road even going up steep climbs, it just spins the wheel out.

I don't get the 800cc thing. Jangly little things with no umph. The 800's are mid to high 30's BHP at the back wheel. the 1000 around 50. No idea why you'd want an 800 at all.

I've had an 800RT. It used to slow down in a head wind. fecking thing. I sold it to Mick Barr who thought it was marvelous. He more than likely tweaked it though (probably turned it into a 1000)

 

[ChasF]

Thanks for the information Rob, what actually needs doing to the heads to make them suitable for the larger bore? I know my existing heads will probably need lead free seats fitted but other than that are they suitable? I don't know about the gearing yet, I suppose I could keep the existing bevel box and fit a +5% or +10% 5th gear. The bike has had a fair bit of off road use since I've had it and back brake is a bit of an issue.

Sacrilege...well, I bought this bike with a view to modifying it. It was not in pristine original condition and I'm not very sentimental about restoring it to original. I had an 84 R80ST in the eighties and went all over Europe on it - I always found it underpowered for long distance use although a nice town bike. My current R100GS, which is still on standard pistons/cam despite good intentions to upgrade, is not as smooth as the 80G/S motor and still a little underpowered. From what I've read it sound like the 1000cc engine with the smaller carbs, high comp pistons and a little tuning makes a good compromise for on and off road use.

 

[Rob Farmer]

Richie Moore machines the head to match the larger barrel. You have a choice of valve and seat sizes depending on what you want out of the engine. To be honest you are much better off contacting him yourself to see whats possible. I went the whole hog with the 80 heads I bought and had the biggest valves I could fit in there along with porting work. In my bitsa 1000 I went for larger inlet valves a small increase in compression and a different cam, the bike has a significant amount of extra grunt as well as a boost all the way through the rev range. It's very smooth as well and really feels like it digs down to it's boots when you put it under load, a feeling that's missing from an 800.

The other option is to keep yours as an 80, fit the higher comp pistons from the road biased bikes and a high torque cam. BUT by the time you have bought a set of BMW pistons your looking at £360 + Vat so not a million miles away from Moorespeed high comp 1000 pistons. my exchange barrels were £120 each + vat but you may have to pay a little more if your exchanging 800 for 1000 barrels - you'd need to contact moorespeed though as you'll get a lot more sense from Richard.

These were the 800 heads after they were taken to 1000. 46mm inlet valves and seats. One piece valves and Calisbro guides. The later 800 heads have more meat in the inlet port allowing tuners to get a better gas flow round the valve, if your not porting then it probably doesn't matter that much. That's a Moorespeed fast road cam at the front which wouldn't suit what you need.

Some more goodies. You can see how nice the re nickasiled barrels are.

Those pistons are a work of art

 

[MikeO]

Richie Moore machines the head to match the larger barrel. You have a choice of valve and seat sizes depending on what you want out of the engine. To be honest you are much better off contacting him yourself to see whats possible. I went the whole hog with the 80 heads I bought and had the biggest valves I could fit in there along with porting work. In my bitsa 1000 I went for larger inlet valves a small increase in compression and a different cam, the bike has a significant amount of extra grunt as well as a boost all the way through the rev range. It's very smooth as well and really feels like it digs down to it's boots when you put it under load, a feeling that's missing from an 800.

The other option is to keep yours as an 80, fit the higher comp pistons from the road biased bikes and a high torque cam. BUT by the time you have bought a set of BMW pistons your looking at £360 + Vat so not a million miles away from Moorespeed high comp 1000 pistons. my exchange barrels were £120 each + vat but you may have to pay a little more if your exchanging 800 for 1000 barrels - you'd need to contact moorespeed though as you'll get a lot more sense from Richard.

These were the 800 heads after they were taken to 1000. 46mm inlet valves and seats. One piece valves and Calisbro guides. The later 800 heads have more meat in the inlet port allowing tuners to get a better gas flow round the valve, if your not porting then it probably doesn't matter that much. That's a Moorespeed fast road cam at the front which wouldn't suit what you need.

Some more goodies. You can see how nice the re nickasiled barrels are.

Those pistons are a work of art

I think I'd leave it at 800cc and have all that kit around my lounge as art...

 

[Rob Farmer]

I think I'd leave it at 800cc and have all that kit around my lounge as art...

Unfortunately, due to a lack of time, that's exactly what I'm doing.

 

[electric_monk]

Unfortunately, due to a lack of time, that's exactly what I'm doing.

Open to insulting offers per chance.?

 

[Sylvester]

I have had a seibenrock on my 800 for a while and yes it does go better but not the same as a 1000cc (I've had both). I like the smaller carbs as they seem to run better and stay in balance longer. My current trusty steed also ticks over like a swiss watch. I started off just servicing the bike and now I have a frame on a milk crate in my garage and stuff all over the place. I have had the head machined to fit the pistons which have also been machined. The Seiben rock pistons have a "step" on them to fit the 800 head. So I have had the barrels/heads and cylinders machined to match. The process was in my opinion very good value for money. But....I haven't yet seen them as they have just been picked up and are in the UK. I will be driving over to pick them up. Also on the list I have ordered a sump extension and a new mainstand coz mine was about to collapse. As soon as it it together we will see what improvement there is.
Next years plan will probably involve getting a 1000cc and tweaking that. All in the interest of scientific research of course.

 

[Sylvester]

Oh and by the way I would tweak it as stock the 800 is ok if you never use anything other than country roads. I found anything else just painful after a while. Overtaking requires a tripod and a telescope. Strangely I had an 800 road bike and that I found ok. Oh well

 

[Rob Farmer]

Open to insulting offers per chance.?

No. The crank and bottom end is off to Moorespeed straight after Christmas for balancing and vapour blasting. It can all go back together then. Just need something to put it in. It would be wasted in a GS chassis

 

[(RIP) Arkwright]

I have had a Siebenrock on my 800 for a while and yes it does go better but not the same as a 1000cc (I've had both). I like the smaller carbs as they seem to run better and stay in balance longer. My current trusty steed also ticks over like a Swiss watch. I started off just servicing the bike and now I have a frame on a milk crate in my garage and stuff all over the place. I have had the head machined to fit the pistons which have also been machined. The Siebenrock pistons have a "step" on them to fit the 800 head. So I have had the barrels/heads and cylinders machined to match. The process was in my opinion very good value for money. But....I haven't yet seen them as they have just been picked up and are in the UK. I will be driving over to pick them up. Also on the list I have ordered a sump extension and a new main stand 'cause mine was about to collapse. As soon as it it together we will see what improvement there is.
Next years plan will probably involve getting a 1000cc and tweaking that. All in the interest of scientific research of course.

Where did you send them for modification?

 

[Ras Thurlo]

I want to take my 1981 R80G/S out to 1000cc. As far as I can see the alternatives are either a Siebenrock kit or standard R100 barrels with Richie Moore pistons. I want to stick with the standard smaller carbs and may fit the enduro cam as I'm looking for a good tourquey engine.

I have the moorespeed pistons and use them on an off-road bike were torque is key.

From what I had understood his pistons are really meant to work with 40mm carbs, but you should check with him what he says about the 32mm.

I had also looked into the 296 cam with his pistons and was warned on ADV about using high compression pistons and this cam. It seems that no-one has tried the 296/moorespeed combo so there is no hard data whether this is an issue.

However there really is plenty of torque on his pistons even with a 308 and 40mm carbs. As Mr Farmer rightly said with a 37/11 final drive will give you what you are looking for. I am currently running my dirtbike with 32/10 and while this is not ideal for the type of dirt riding I get to do around home (more technical enduro than desert blasting) the engine has enough grunt to deal with this wrong gearing.

In terms of heads you will need to modify them from your g/s 80 heads. My dirtbike has 44/38 valves on r100 heads, this gives you a bunch of power further up the rev range. My citybike also has his pistons and I have so far had been using stock r100 heads with no mods, this gives you similar low power but far less above 5k revs. For this city bike I have just had richie do up a set of heads with 42/38 valves + porting. The intention behind this was to give a longer pull, but did not care so much about absolute high end power so kept the smaller 42 inlet. But have not tried them yet.

No experience with Siebenrock, but from what I had figured out from various sites is that the upgrade kit (80 to 1000) does not give such a performance hike for the cost, while the upgrade kit (100 to 1000) is a far better piston. But in order to make the upgrade kit work on an G/S you will need to get 100 carbs+heads anyway, so at that point you might as well go Moorespeed.

hope this helps

 

[ChasF]

Thanks Rob and Ras. I will be getting in touch with Richie in the next few days. Current thoughts are, as per Rob's engine, to go for the exchange barrels and modified existing heads (valve sizes following Richie's advice) and stick with the 32mm carbs. I'm not looking for a race engine revving to 7500 as Richie's higher performance motors do. I would like a decent compromise between road and off road performance - something that will cruise comfortably at 75mph, given the limitation of the tyres which will probably be Mitas Knobblies, and will be torquey enough to deal with moderately technical European trails without worrying too much about gearing.

To achieve a comfortable cruising speed at around 4-4300 rpm I'll almost certainly either need to raise 5th or fit a higher FD (or possibly both) but my theory is that with a tractor engine I won't even notice a 2.5% increase in the FD off road although it can make all the difference on a KTM.

 

[Garry H]

I like the Siebenrock kit
Big improvement in HP and torque..
I have gas flowed the heads a small amount on mine and it goes as well if not better than my R100GS ( maybe cuz it lighter )
It pulls clean from low rpm with more usable low down power than the R100
It is plug and play...Works very well with the standard head and 32mm carbs
Plus i have done over 30k with one kit with no trouble with reliability
On a standard monolever G/S i found the kit was more than enough ( too much to be honest ) for the brakes and suspension
I removed the kit when i sold the G/S and fitted it to my R80 Basic... It is a much better match for that bike
I would not hesitate in going down the Siebenrock route myself

 

[ChasF]

Garry, I think you are saying that 80G/S heads can be fitted straight onto the Siebenrock pistons without any machining or modification. This is what I had understood to be the case although it may not give the best results. I'll ask Richie what needs doing to the heads in order to fit his pistons.

 

[Garry H]

Garry, I think you are saying that 80G/S heads can be fitted straight onto the Siebenrock pistons without any machining or modification. This is what I had understood to be the case although it may not give the best results. I'll ask Richie what needs doing to the heads in order to fit his pistons.

Siebenrock kit is plug and play
It's a couple of hours work tops no other mods and it works and is as reliable as stock
It is designed to work with stock heads
Like i said mine has covered over 30k...It's still fine and has done a fair amount of road and off road
Spain

Uk

Croatia ...Same kit different bike