swapping vintage carburettors for modern ones, will it make more horsepower.

[Marc.com]

 
No doubt the bike will probably make more hp with a new "modern" carb, BUT will you go faster?
When I was young I fell for the bullshit and changed the carb on my KTM. The motor went POP, so I changed it back and had no problems after that.
[/quote]

Yes you probably will go faster with more and smoother power, which is why modern carbs are not allowed in most VMX racing. Modern carb like FCR jetted correctly will perform like night and day compared to older factory carbs.

As for the carb making your engine go pop, no substitute for jetting it right.

[Mike52]

As for the carb making your engine go pop, no substitute for jetting it right.

No argument there.

[Marc.com]

I remember my own 89 KTM350 ran like shit when I got it, the difference between very clean jetting and piss poor bottom end was one needle clip position. since then I have been prepared to spend the time to jet them right.

Some carbs also are more jetting sensitive than others so that helps to confuse the issue. Small changes on the Dellorto PHB seem to make a hell of a difference.


 

[LWC82PE]

For what its worth, i would go the way Frosty is going and fit a 38mm flatslide to the PE400 or maybe a 36mm if you want a bit more fuel enconomy. If flat slides were no improvement over the roundslides then they wouldnt make them. Yeah i know 99% of people would benefit from a riding school or newer suspension but wheres the fun in that. Bog standard bike rebuilds are boring, half the fun is in making your bike look personalized and enjoying shopping around for different parts you can add or change. What ever carby you choose, just make sure you pick a oil ratio (preferably what the bike manufacturer says) pick an oil, pick a fuel (preferably a high octane one) and then spend the time to get the jetting right to suit that and then dont change anything except if you maybe riding at different altitudes or to suit different temperatures or the type of course eg fast open or tight twisty.

[DR]

Comparing an old worn carb against a new carb (even of identical size) is like night and day. I've done a couple of swaps in recent years on TM's and RM's and as others have stated, there doesn't seem to be any more outright HP but the throttle response throughout the entire rev range improved out of sight

[Captain Bilko]

I'm all for replacing old worn out carbs for new (of the same type). Saves a ton of head-aches.
I just feel people are giving themselves (and more-so the next owner after they've given up in disgust) a huge head-ache by trying to retro fit stuff in the vain (very) hope that they're gunna go faster.
Sure bikes have evolved in the last thirty years. Those titanium valves outa late model YZF's must be the ducks nuts! Why not try cable tying a coupla them to your swingarm and see if any gains are made there.....

[Marc.com]

I just feel people are giving themselves (and more-so the next owner after they've given up in disgust) a huge head-ache by trying to retro fit stuff in the vain (very) hope that they're gunna go faster.

Whether I ride fast or not I like to improve and mess with my bikes. Its only a headache if you don't know what you are doing and I don't give a shit about the next owner.

I like to replace heaps of stuff for reasons other than going faster, racing has been always about modification and having cool stuff. Look at MX even today, as good as the bikes are there are still a lot of modifications and the fast guys rarely ride stock bikes.

[Captain Bilko]

Its only a headache if you don't know what you are doing

We'll leave it there then shall we?

[PE MAN]

do you think my old man will notice if i take off a delotoro from his duke leight  think once there is some more cash in the bank might either try the 38mm mikuni like frosty or go with a 36mm bing.

[VMX247]

It may have been covered in this thread or some where else but what is the ruling on later model carbs or the GCR's for racing purposes are you allowed to fit a carb that was not available back in the day?

#8

FOR Classic and DT --If you have this years MA/MOM/GCRs have a read of 18.6.0.4--------- KIS
cheers A

[number8]

It may have been covered in this thread or some where else but what is the ruling on later model carbs or the GCR's for racing purposes are you allowed to fit a carb that was not available back in the day?

#8

FOR Classic and DT --If you have this years MA/MOM/GCRs have a read of 18.6.0.4--------- KIS
cheers A

Took a look ,thanks was I being a bit lazy really,

#8

[head]

If you buy a new VM mikuni round slide, do you run it with the jets supplied as a starting point? Or do you have to buy the same needle, needle jet, main, pilot etc as was in your model. What I am asking does the carby work off the shelf with some fine tuning or do you have to make it identical to one removed as the jetting is very different.

[rohan]

You may be able to run it off the shelf as a starting point but it will be just that a starting point. I have found a lot of suppliers will set up the carby for you if you give them the specs from a workshop manual, that is assuming you are running a stock engine.

[Captain Bilko]

I bought a 38mm Mikuni for the YZ 465 from that mob in Qld (sorry, can't remember the name off the top of my head) and they sent it jetted as per the Yamaha manual. Very happy with it I was.

[Tim754]

Mikuni?  T D Hatrick and co QLD??  or is that for Holley carbies?