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overland and classic
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Discussion Starter · #42 ·
Mikey boy, I'm interested to see how well the DS650 piston goes in. I've recently been drooling over the 730cc big bore kit at OMW Racing ( for my '03 Dakar ). Not convinced though as it would be difficult to increase fueling with the FI. It might be possible to bore out the throttle body a little, and go with a larger injector. Or perhaps a gs1150 or other larger throttle body could be persuaded to fit. The kit should fit the funduro better, and it would be easier to increase carb size too. Obviously it would mean new exhaust etc.....where do you stop?

Keep it coming, also love to hear of any other rotax engine mods you might know of!
i have no idea if it would be compatable with a dakar/gs as they have a different cylinder head and already run at 11.5 to 1(so i doubt it).i think the twin port funduro engine is a far better basis for mild tuning and good power gains per£££.regarding tuning the dak/gs fi engines i think your gains will be made with the fueling and ignition mapping so a programmable ecu would be the first investment .if you did decide to bore the engine ,maybe you could improve the fueling with a different injector or maybe just increase the fuel pressure,as you say where do you stop.at some point you have to decide whether it may just be a better idea to buy a ktm :think::nono:
 

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yes it is,it should fit with no modifications.but i need to check squish clearances to be certain.
The piston from Team Pami 12:1 requires squish machining http://www.team-pami.com/cms/?q=en/node/690, apart from the price of itself
Does stock rings fit DS650 piston? It seems to me this is effective and simple upgrading which adds some more power to F650 Rotax derated engine. Really interested to know how it it will work. Presumably it may require rejetting
 

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overland and classic
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Discussion Starter · #44 ·
The piston from Team Pami 12:1 requires squish machining http://www.team-pami.com/cms/?q=en/node/690, apart from the price of itself
Does stock rings fit DS650 piston? It seems to me this is effective and simple upgrading which adds some more power to F650 Rotax derated engine. Really interested to know how it it will work. Presumably it may require rejetting
the piston i have bought is not a stock ds650 piston but a high comp one from america,it comes with rings and gudgeon pin.,why would a rejet be needed? the displacement hasnt changed!..having checked clearances today it is a straight swap:):)
 

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Always wondered, how come? carbed F650: compression ratio 9,7 - 48hps, injected F650GS 11,5 - only 50hps...:think:
Yeah, 09 G650GS claimed 53hp @ 7000rpm. Unless they changed measuring stds over the years, that's 5hp, almost 10%. There must be a couple of ways to increase power from these engines without too much stress. OMW racing claim a 6hp increase for an alloy intake port and single 48mm carb for the DS650. Perhaps a slightly wider throttle body and a rigid intake would do the same for the FI bikes? Do you think there could be any loss from the collapsing rubber manifold?

Apologies Mikey boy for hijacking your build thread.... but it does kinda tie in with what you're doing?

PS: Who makes the piston you've sourced?
 

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To my shame I have never worked with FI bikes and also have never ridden F650GS or G650GS, so I can't compare them to carbed Funduro. But I rode Jawa Rotax 650, it has the same engine as DS650 and one Bing carb. No low end at all. Seems like it lacks fuel.
I don't think there is any loss due to rubber manifold. Twin carbs work excellent.
I meant: such a difference in compression ratio and only 2 hp gain... (about F650GS '00-'04) Maybe it is FI, cat and lean mixture that restrain this engine. With nearly the same engine Husquarna Terra has 58 hps!

Sorry for making offtopic posts in your thread, Mikey boy
 

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overland and classic
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Discussion Starter · #48 ·
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my seat has come back from tony archer:mrgreen:resculpted to remove the step at the back.top job!!!
in response to previous question.the piston kit is from JE pistons but i cant see it fitting a dakar,the FI engine has more than enough compression ,it needs to breathe!take a look at the dakar race bikes exhaust system !!apparently they ran the motors in stock trim;)
 

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I like that seat! Blue looks good with the white bike too.

Just checked out je pistons. I see they make a 5mm oversize piston too ( same compression ) that gives 720cc.
I'm presuming the piston you got increases compression by increasing the piston "compression height" ( distance from pin to top of piston ), as I assume you use the same rod, gaskets etc as stock ? Any chance you could measure them when you change pistons?

The reason I ask is I'm wondering how BMW increased the compression on the later bikes, if they did the same then cylinders should be interchangeable between models ( and perhaps the ds650 too - that would mean DS big bore kits would fit too! ) If they changed the deck height then the cylinders would be different heights and not interchangeable ( assuming the rest of the engine stayed the same ). I'm guessing it's the piston that changed as that would be the cheaper route I think.

Any theories?
 

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overland and classic
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Discussion Starter · #50 ·
I like that seat! Blue looks good with the white bike too.

Just checked out je pistons. I see they make a 5mm oversize piston too ( same compression ) that gives 720cc.
I'm presuming the piston you got increases compression by increasing the piston "compression height" ( distance from pin to top of piston ), as I assume you use the same rod, gaskets etc as stock ? Any chance you could measure them when you change pistons?

The reason I ask is I'm wondering how BMW increased the compression on the later bikes, if they did the same then cylinders should be interchangeable between models ( and perhaps the ds650 too - that would mean DS big bore kits would fit too! ) If they changed the deck height then the cylinders would be different heights and not interchangeable ( assuming the rest of the engine stayed the same ). I'm guessing it's the piston that changed as that would be the cheaper route I think.

Any theories?
the later gs/dakar still have a flat topped piston crown,however the cylinder head is completely different(single port)this is where the hike in compression has come from,the cylinder head on a funduro and the bombardier is rotax but the head on a gs/dakar is bmw.i have never removed the head from a dakar but would suspect that the squish clearances are a lot tighter ,basically meaning that none of these tuning bits will be compateable,one of the other stumbling blocks is the nicasil bore,to fit an oversize piston i would think you will have to machine the existing liner completely out and fit a new one.if someone with deep pockets wants me to strip their dakar and get more poke out of it i would be happy to help out:cool:
 

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That makes sense. I'm aware the head changed but forgot about that possibility for compression change. If that is the only change then cylinders should be interchangeable. I've found two DS big bore kits ( one a resleeve, the other a completely new cylinder ). It seems the latter might be easier. If not correct deck hight could easily be adjusted by skimming to decrease, or adding a base gasket shim to increase. Not cheep though! I've heard of one big bore F650 on ADVRider, but haven't been able to find any details on it.
 

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That makes sense. I'm aware the head changed but forgot about that possibility for compression change. If that is the only change then cylinders should be interchangeable. I've found two DS big bore kits ( one a resleeve, the other a completely new cylinder ). It seems the latter might be easier. If not correct deck hight could easily be adjusted by skimming to decrease, or adding a base gasket shim to increase. Not cheep though! I've heard of one big bore F650 on ADVRider, but haven't been able to find any details on it.
take a look here http://www.team-pami.com/cms/?q=en/catalog/52/bmw
 

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Yeah, they are, seems to me their parts are made from gold :) But if you, guys, look up the info of the kits they offer, and exclude 4 hps, that carbs with fuel pump can add, you will be able to see, how power and torque will be changed by tuning the engine;)
I talked to them when I intended to install carbs with fuel pump, just to know what I could get if I would do that. But then I dropped this idea. They told me that I should also change the clutch spring for the stiffer ones. But the springs from them cost a fortune. I'd rather buy for 10 quid the EBC ones
 

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I would rather leave the clutch springs stock. F650 FAQ's have rumors about stiffer clutch springs causing the splined shaft & push rod thingy to strip or break splines off. Perhaps if you go the 90 hp route you would need upgraded springs to stop the plates from slipping......
 

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I would rather leave the clutch springs stock. F650 FAQ's have rumors about stiffer clutch springs causing the splined shaft & push rod thingy to strip or break splines off. Perhaps if you go the 90 hp route you would need upgraded springs to stop the plates from slipping......
I have seen F650 FAQ. I don't know which springs they installed to have splined shaft and push rod, but one of my friends with F650 '97 installed the EBC ones. 2 years without any problem. These springs are just a bit higher than OEM, about one more turn of coil, but when you pull the clutch there is no feeling they are much stiffer.
If I go the 90 hp route I should buy not only the springs but also heaps of Team Pami parts for it to have in reserve cause so heavily modified engine won't live too long...;)
 

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overland and classic
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Discussion Starter · #59 ·
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my fabricator has been busy again:D,this is my prototype rack ,as i have no intention of fitting indicators to this bike!
i could change the design to accomodate indicators if any one wants one.:whistle:
i just wanted hand holds for dragging the back of the bike around and somewhere for a basic tool kit/tubes etc;)
 
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