I'm getting ready to do a wiseco reverse dish piston conversion on my 94 883 and was wondering if I need to replace the valves with 1200 valves or do I need to just leave it alone. I know the conversion doesnt require any headwork, but I've also been told that replacing the valves and a little porting and polishing would get me more from the conversion. I'm just looking for a good street-riding bike, nothing radical. I've also been told that a 1200 ignition module would be beneficial. I'm keeping the stock cams. Thanks for the help beforehand. I searched through the archives and didnt find my answer, hopefully somnebody can help me out.

G'day

Changing to 1200 valves and using the dished piston means you HAVE to use a conversion valve.... Black Diamond has some and I think a couple of others do too...

This require the seat be cut out to suit the larger valve and is NOT a job you can do at home....

What you can do is to remove the heads and you can remove the valves and clean the heads up.
A new set of 883 valves and take the bare heads and the new valves to any local reputable engine re-conditioning business (or better still whoever is boring your cylinders out) and get them to re-cut the seats to suit your new valves. (you could also do this to suit the 1200 conversion valves but it leaves a bit more material in the step area, starts to get a bit trickier but still not difficult if ya just after a bit more power)

If the valves are not badly pitted you can get them to re-face your valves which will be even cheaper...... I would expect that the pitting in the valves. especially the exhaust would be too bad to re-face tho..with it being a 94 and being 883 for so long.

when you have the luverly new seats you can just blend the steps between the valve inserts and the head...

This will give you best bang for buck low end...


The 883 ignition module is fine..... you may have to adjust your timing and this is done with the hall sensor pick up behind the timing cover on the right hand side..

I'm looking at the Manley 1200 conversion valves if I decide to replace the valves.

nothing wrong with them...

Black diamond valves are a little cheaper than manleys. Which is the better valve? I dont know dick about either one. Or is there a better one out there?

Take ya pick... I'd go with Black Diamond if it was mine... the coating is good

I'm getting ready to do a wiseco reverse dish piston conversion on my 94 883 and was wondering if I need to replace the valves with 1200 valves or do I need to just leave it alone. I know the conversion doesnt require any headwork, but I've also been told that replacing the valves and a little porting and polishing would get me more from the conversion. I'm just looking for a good street-riding bike, nothing radical. I've also been told that a 1200 ignition module would be beneficial. I'm keeping the stock cams. Thanks for the help beforehand. I searched through the archives and didnt find my answer, hopefully somnebody can help me out.




Definately go with the 1200 valves as well. The engine will already be apart and it will save you a tear down fee doing it later if you are having it done professionally. The smaller 883 valves wil render your spanking new cylinders somewhat anemic and you will not get the full performance you seek. You're basically pissing up a rope if you don't do valves too.

The smaller 883 valves wil render your spanking new cylinders somewhat anemic

I've been led to believe that using the stock 883 heads will give some added torque vs hp at the top end with valve work. Torque being the usable ooomph on the street. That being said, I'd advise leaving the heads alone if all yer interested in is street performance. Just my .03 cents worth.

Thats what I heard too -- I'd really rather have the torque

I've done a few 883-1200 conversions....

A LOT depends on what the customer is after, I did one the other day and just cleaned the steps up were the inserts meet the head..... Kept the stock 883 valves with a valve grind.

The bike works well for what the customer wants.... it will accelerate well enough to overtake safely from 90klms in top gear....

the bike will NEVER be reved past 4000. so why waste money trying to make the engine breathe where it is not going to be used....????????

The customer is happy and it accelerates faster than her Dyna.... :)


If ya wanna get up the revs and will be running it past 4500 then the 1200 conversion valves are a good idea...


Port size and valve size are only an issue when they become a restriction ... and that's NOT an issue below 4500...

i'm with willprevale when it comes to street performance - though i must admit that's mere "understanding the theory" that makes me believe this. i think beyond a certain "throttle point" you'll benefit more from the bigger valves as the smaller ones will just restrict the flow acting like a limiter - that again is theory - sorry, i've got no experience so far that makes this a certainty.

i'd say this is also a question of the rpm-range you'll be drivin at most of the time -but please all others correct me if that - in your opinion - is nonsense.
k

I would think that if you are going to leave the 883 valves in you might as well leave it an 883. It has plenty of torque and zip for around town. A smaller valve will let in the same gas air mixture, giving a smaller explosion in a larger combustion chamber. How does that improve torque wich is generated by the downward stroke of the piston? Seems it would be better just to go with high lift cams and not even bother with conversion. The reason I'm doing the conversion at all is to have more roll on speed for passing on the superslab.

i'd say this is also a question of the rpm-range you'll be drivin at most of the time -but please all others correct me if that - in your opinion - is nonsense.
k



I have never been afraid of putting forth nonsense :laugh :laugh

oops, seems stevo was quicker with writing down the same thoughts...i just entered sleep mode :p
well, i don't mind sharing an opinion with someone who has converted more than one sporty!
and stevo, you mustbe right, cause your advice is why i didn't change valves! :laugh

Port and valve size are only an issue when they become a restriction to the flow..

If your 883 will rev freely to 5500 with the stock valves and ports

and you increase your capacity to 1200 then the amount of airflow at 4100 will be about the same as at 883 at 5500.

If you can get the air to flow faster at a given revs then the gas charge has more inertia and will fill the cylinder better.....

This usually equates to better throttle response and fuel burn...

The best port/valve/carby combo is the SMALLEST one that will do the job properly.....as this keeps gas speed up

Unfortunately this "job" changes from customer to customer and is one of the reason you will normally see me ask 20 questions BEFORE I say much on what to do



If you are not going to go past that point very often if at all then it makes no sense to build it for top end....

If you like to rev the motor than that's a different story..... if ya REALLY like to rev it then buy a jap bike..

I've found that most people don't rev their Harleys much

well, desertfox, there you go! just switch the viewpoint and everything has a different action.
i'm just gonna throw in another bit of valve idea : the way you puy it makes changing the inlet valve only more reasonable.
now i dont know what local time YOU have , i certainly am going to sleep.
c u tomorrow.

I have immense respect for anyone who can do the Sporty conversion. When I was getting bids on mine I found plenty of people who would do just the cylinder/piston swap out. But as long as I was doing it, I figured I might as well go whole hog (pun intended) It doesn't make sense to have your bike torn down twice if you're going to do it anyway. Save yourself the price of a new set of head gaskets and have it all done at once. I mean sure, you can get by quite well with a simple swap out, but why bother if you're not going to go all the way? I plan on doing cams eventually as well, but that CAN wait. I can do that later and will not have to have the heads torn off the engine to do it. In case you haven't guessed, I want a GADDAMM BELLOWING THUNDERHAMMER :laugh :laugh :tour :headbang

I agree with the idea of smaller valves getting more in at lower revs. As I understand it the smaller area means that the higher vacuum created as the piston goes down increases the velocity of the charge flowing in so that for a given time more air and fuel will be in the cylinder when the valve closes.

This was the reason behind Honda's VTEC on the late model VFRs which only used two valves up to 7000rpm and opened all four up from there. There was a demonstrable improvement in torque below 6000rpm.

What I am interested to hear opinion on is getting the std 883 heads flowed before putting them back on. Is it worth the money and the effort?

Roger if ya gonna spend the sort of $$$$$$ to port them then the valves are a bottleneck .... it would be a waste of $$$$.... without doin the valves


One needs to work out WHAT you want from the engine before you start tryin to put the cart before the horse...

An engine is an air pump and a system at the same time......

What you wish to get out of it becomes why and what you do to get that figure is the how...

ya need to know why ya doin something before ya figure out how..... theory and then experiment


at the end of the day the goal is not to get the heads flowed it's to get the bike to run a certain way....

If you like to rev the motor than that's a different story..... if ya REALLY like to rev it then buy a jap bike..

I've found that most people don't rev their Harleys much


First of all there is NO excuse for buying a Jap bike. Geeze. As for What MOST people people who own Halrley's do.......... well MOST people don't even ride them other than weekends . The phenomenon of the Harley owner who buys it and leaves it garaged most of the time is well documented. This is particularly true with BT owners. Stevo's right. Figure out what you want from your bike first, then go for it. AS for blowing away BT's at red lights, my Annabelle (883 taxes paid) did that with ease. The bottom line is this: the 1200 engine comes from the factory with 1200 valves for a REASON. I think the engineers at H-D knew what they were doing. If 883 valves will choke off performance at high rpm, it will choke it off at low rpm. It's just that at low rpm the effect will not be as pronounced. And with the increase in torque at the low end it may seem you are getting the whole package but you will ultimately be disapointed . Can you *get by* with just cylinders? Sure. But why settle?