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Discussion Starter · #1 ·
Hey guys and gals,

Found a 98 M750 with 7k miles on it that second owner says has Fast by Ferraci hi comp pistons. Says bike runs good but thinks carbs or "dirty" as he hasn't ridden it much. He's basing that on the fact that it is cold natured on first start up. Wonder if the dang thing has some FCR's on it too. ;D Was wondering if anyone is running hi comps on their 750 and if so what could I expect as for as power/torque goes. May try look at the bike tomorrow. Any thing I should check or concern myself with as for as the hi comps go? Bike is at a good price as owner says it has not had it's 6k mile service.

Thanks!

Mark
 

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I had the FbF hi-comps in my 750ss and loved it. noticable increase in torque over the stock compression. I actually ran the stock gearing until just recently and was still able to pull power wheelies and break the rear tire loose exiting corners, both of which were just a pipe dream before the pistons. As far as the rough running, pick up a set of NGK DPR8EA-9 plugs and take with you (and a plug wrench). If he'll let you, swap the plugs and see how it runs, The hi-comps tend to lean foul plugs if the mixture isn't richened (something about better conditions for fuel burn). I had to replace the plugs on mine about every 3k until I finally LOOKED at them and went to a fatter main jet, then I had no prablems at all. If the bike still has the O.E. :-XChampion:-X plugs in it, I'll almost guarantee that this is the problem. The Duc shop I worked at used to replace the Champions with NGK before ever firing the motor.
 

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Discussion Starter · #3 ·
Hey, thanks for the great info! I emailed owner again last night and haven't heard from him. I guess he may have sold the bike. I'll let you know what I find if I can get down to look at it.

Mark
 

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I rode a 750 with high-cops this past week, just a quick ride. I loved the way it felt v.s. my stocker. In general I would say it was much "fatter" all over v.s my bike.
 

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In my 97 M750 I have Hi-Comp's, 39mm FCR, DP Flywheel, Dyna coils and good wires.... cleaned up valve seats a bit too.
71.6 HP.... stock gearing and it definatley wants to wheelie !! Impressive performance..
 

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not to hijaick this thread, but DucSea, what is the yellow bike in the background of your avatar? is it a naked supersport?
 

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How "difficult" is it to swap out the pistons on an M750?
 

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How "difficult" is it to swap out the pistons on an M750?
You can do the pistons without splitting the cases (watch you don't drop the gudgeon pin circlips down inside though!), and you could _probably_ do it without removing the engine from the frame, though it'll be _much_ easier on the bench.

So you need to drop the motor out (or remove from the frame everything from the motor up), take the belts off, then pull the heads off and then the barrels. Then the pistons are just sitting there waiting for you.

The scaryest thing for me was making sure I got the cam timing right when I put it all back together... It all went fine in the long run though, just take your time and double check all your double checking... (preferably have a competent friend double check for you as well)

The other thing I got told to be extra careful with was making sure you get the oil rings into the barrels carefully, apparently they crack pretty easily, and you can't buy the oil rings on their own, so you have to buy another ring set if you break them (this didn't end up being a problem for me).

If you do it with the engine on the bench, its pretty easy to use a ring compressor, I'm not sure mine would fit easily on the vertical cylinder with the motor in the frame...

I also found it easier to put the pistons(and new rings) into the barrels then put them on the rods, rather than try to get the pistons into the barrels while attached to the rods as the Haines book-of-lies suggests.

big
 

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not to hijaick this thread, but DucSea, what is the yellow bike in the background of your avatar?
 

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I know some pistons require honing the cylinder. Can anybody explain?
Not the Monsters - they've got nikasil coated cylinders - they "just don't wear out" according to my local guru, "you either damage them with broken valve or ring bits, or they're fine".

big
 

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Not the Monsters - they've got nikasil coated cylinders - they "just don't wear out" according to my local guru, "you either damage them with broken valve or ring bits, or they're fine".

big
The BCM Pistals 12.1:1 do need a little bit of honing, according to Bruce.
 

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I am running stock Champion RA6HC plugs in my 1996 900 with hi-comp pistons, stage 2 jetting, K&N filter, and NGK racing coils/wires. I went to the auto store today and picked up a set of NGK DPR8EA-9 plugs. Can I use these, or do I need to get them to order the DCPR8E plugs? What's the difference? Thanks!!
 

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DCP family usually have solid plug top, which is not compatible with the spark plug wires. Stick to other D family, like D8EA or DP8EA-9.

:) Chris

I am running stock Champion RA6HC plugs in my 1996 900 with hi-comp pistons, stage 2 jetting, K&N filter, and NGK racing coils/wires. I went to the auto store today and picked up a set of NGK DPR8EA-9 plugs. Can I use these, or do I need to get them to order the DCPR8E plugs?
 

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-----------------snip-----------------------
The other thing I got told to be extra careful with was making sure you get the oil rings into the barrels carefully, apparently they crack pretty easily, and you can't buy the oil rings on their own, so you have to buy another ring set if you break them (this didn't end up being a problem for me).
------------------snip-------------------------
big
True words. I've BTDT on the oil ring...... :'( They are very fragile. I got very lucky and caught the broken piece before it fell into the bottom end.
Fortunately, I was able to source a used oil ring from a local independent Duc tuner. Good thing, 'cause none of the dealers in LA had any rings in stock :mad: .

Use a ring compressor.
 

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NGK dcpr8e plugs will work fine as a replacement for DPR8EA-9 as long as you get them with screw off/on terminals (parts unlimited sells them both ways). the biggest difference is that the DCPR8E is a 5/8 plug vs. the DPR8EA-9 being 18mm.

the bigger possible problem is that both plugs are projected reach plugs and your hi-compression pistons might be tall enough to close the gap for ya. :eek:
if you want to be safe with a ngk plug try a D8EA(18mm)
these should work well as long as you have the stock plug wires/caps
good luck
 
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