851 Upgrade Motor Options?

Corse

I know the ST4S seems to be the the choice of some to upgrade but interested to hear if anyone has seen or know of others?

hauge

Corse wroteI know the ST4S seems to be the the choice of some to upgrade but interested to hear if anyone has seen or know of others?

Depends on what you are after. I bought a slightly crashed st4s together with a friend of mine. I´m going to use the engine (look on projects). Wheels and stuff is also usable (with modification) depending what you need and like.
I ended up with aprox. 1000 euro fo a completet engine, but it will probably end up 3 times more with porting, pistons, camshafts, rods etc......
At least in europe the st range seems to have lost interest on the market so they are cheap now.

Cheers
Thomas

Corse

I am considering picking up a S4R motor with swingarm, I believe the suspension setup maybe different linking to the frame but have not had chance to study that option, just seeing if anyone else has.

marvin

Corse wroteI am considering picking up a S4R motor with swingarm, I believe the suspension setup maybe different linking to the frame but have not had chance to study that option, just seeing if anyone else has.

The S4R should fit just fine with the 851/888 swingarm. (isn't it basically a ST4s engine?) I slowly putting a S4RS in mine which is a lot more work. Some early pics and discussion in the projects section here.
There are also pics of another chap putting one in his bike.

Corse

marvin wroteThe S4R should fit just fine with the 851/888 swingarm. (isn't it basically a ST4s engine?) I slowly putting a S4RS in mine which is a lot more work. Some early pics and discussion in the projects section here. There are also pics of another chap putting one in his bike.

So I guess the single side swingarm will not be an straightforward "bolt up" ?

marvin

Corse wroteSo I guess the single side swingarm will not be an straightforward "bolt up" ?

I'm not all that familiar with the suspension setup on the S4R but I really doubt that it will be a straight bolt up.
But, shouldn't be all that difficult to do. Have you compared lengths of the two swingarms? If the S4R is longer that might be a good thing! I roughly measured the length of a 888 corse swingarm and it's about 15-20mm longer than a stock 888 swingarm.

Are you sure that you wanna change the looks of an 851/888 that much! 😄

stafford

You can certainly swap an S4R into an S4 Monster, which although it does not have the hoop it is a similar swing arm to the 888.

Corse

Not measured but I heard it was longer, whats the length on the 851 swingarm? I am trying to buy back a 1990 851 that I owned in 01 used as a trackbike, sold it 3yrs ago and its sat since. The bodywork has been repainted but I was thinking of a radical change in suspension, brakes and motor.

got2dv8

stock 851 swingarm is approx. 580mm

Robert

Corse

Thanks going to check on the S4R swingarm specs to compare

Macca

wont the 851 swingarm fit the S4 cases ? or are these more like the 916 cases using the frame as outer swing arm axle support

marvin

Macca wrotewont the 851 swingarm fit the S4 cases ? or are these more like the 916 cases using the frame as outer swing arm axle support

Same as 851/888.

Corse

The rocker "looks" offset on the S4R frame, I am concerned that while the S4R swingarm will bolt up it won't line up at the top but I need to check closer. I guess the alternative is using a S4R frame but that means more work possibly.

Jimmy

I'm doing the st4s motor swap, using 996sps parts (alternator cover and flywheel-dual ignition pickups) so that I can use a p8 ecu.

got2dv8

Can you elaborate more about using the p8? As opposed to what other ecu...? I am considering using a p8 on my 851/888 project motor and would like to know if any bottom end mods are required (ign/timing).

Robert

Jimmy

No mods needed with a 851 motor, The st4s motor has only one pickup for the timing, I could have use the 1.6 ecu but didn't want to change the wiring harness so I could put the original 851 motor back in one day

Corse

Ok so now I have done it..yesterday I picked up an S4R motor kit, swingarm headers and other parts left over from the damaged bike and then only 30 mins ago I cemented the deal to get my old 90 851 back this Saturday. Now the fun begins. I know this may be over the top for some but I am thinking of not only putting the S4R motor in but the swingarm too, with mods , the front end will have to be modified too, not sure yet but will be updated and keeping the bodywork stock except for 888 carbon tailpiece I am also picking up as part of the deal. The frame is going to be powdercoated aswell, colors to be considered but I may go back to stock white or try red- will see.