Triumph Rat Motorcycle Forums banner

1 - 20 of 47 Posts

·
Registered
Joined
·
38 Posts
Discussion Starter #1
hi @ all


i am new @ this board and wanted to say hello to all. i didn´t find an "entrance" where all new users can tell a little bit who they are and where they are from...so i do it here

i am from germany and got a scram since 4-5 months...before i had a 1050 S3 + 675 daytona...both are fine...but i want to take it easier while riding the bike

evenmore there are so many nice parts on the market to build up your own individual bike...and therefor here´s my first question:

did anybody make any experience with those flatside-carbs? sorry...page is in german...but the pics must be the same in english ;) :

http://www.mikuni-topham.de/DEUTSCHSITE/Galerie/Sonderanfertigungen.html

u gotta scroll down the bar to see the triumph-carbs...those are in 36...but u can get them up until 48...look here:

http://www.mikuni-topham.de/DEUTSCHSITE/TM_4-Takt/TM_4-TAKT.html

advantage of those 36:

low price with round about 600,-eu which is almost the same in gbp

disadvantage:

the slide isn´t with wheel bearings


so u can save almost 400,-eu instead of the keihin fcr and especially for the scram i think the 36mm carbs would be enough to keep torque where it is...directly at idle up to 5000rpm...that´s all i need


any answers that can help me out?



cheers


twinfan
 

·
Registered
Joined
·
1,498 Posts
I believe bigger carbs. make bigger hp at higher revs. but smaller carbs. are better for mid range. I guess it depends what you want from your bike, not everyone wants to ride at WOT. I cant see the 36mm flat slides being any great advantage over the CVs though.
:confused:
 

·
Registered
Joined
·
38 Posts
Discussion Starter #5
you´re right...smaller carbs are better for low torque...and that´s why i have the scram and not a bonnie/thrux...and i just want to keep it like this, when installing flatsides

i just want to know if bigger carbs are better especially on a scram with it´s very mild cams...i don´t know if it works so good on those cams with 6.5mm lift on the inletside


but...

i think i have to tell you that there is 904kit and headwork inside my scram...and i read the thread with changing the cams in a scram with those of a 790 speedmaster...but i just think i don´t need that & can save the money...so i just want to get a feeling by asking you what might be best for my wishes - which is low end torque


i got a good book about carbs which has a graphic that shows:

when u want about 35hp from one cylinder (which is roundabout my aim) you need a 36mm slide-carb and a 40mm carb like those CVK´s with membrane (don´t know the word in english for that carb-construction with membrane...maybe anybody can tell me so that i learn :) )

so what do you think is best with my constelation of 904kit with headwork (still std-valves), when i don´t want to change cams and keep the torque just there were it is? i don´t care about more hp at higher revs...it has to work from idle up to 5000-5500rpm...that´s it



generally it is a simple calculation:

the hsr carbs are about 1450 usd...since i got em here they are almost 1900 usd because of taxes and fees which is 1350,-eu

those 36mm TM-flatsides are about 600,-eu and maybe the 40mm are at least 700...you can have them even bigger up to 48...so...why spending so much money on a hsr or FCR?


kind regards


twinfan
 

·
Registered
Joined
·
1,995 Posts
Those Mikuni 42mm carbs do not just make power in the upper revs...they make power everywhere throughout the curve. This will be especially beneficial as you already have an 904 kit installed.

You will get far more bang for your buck out of carbs when compared to cams. Cam's are a sort of voodoo that noone seem's to have solidly figured out. For the 790/360* motors the '01 bonnie cams seem best to this point. Carlo's has some 813's that seem to be building power..


I installed 42mm Hsr's and gained 8 rwhp..with side covers intact and K&N filters. Unifilter's breathe far better..and I am pretty sure they are cheaper than K&N's.

I also have a 904 kit, exhaust cam advanced 1 tooth, pro-com unit, airbox elim, flow work to the head..( stock valves )..free flowing exhaust.

While the 36's are far cheaper..you wont get nearly the same end result...save your penny's.
 

·
Registered
Joined
·
8,872 Posts
the 42mm on a stock motor pick up more ft/lbs then hp .They pick the bottom up as much as the top or more so.The first thing that stood out to me was idleing going down my drive way a quick1/4 throttle the bike will jump sideways.Stock carbs wouldnt do that.Thats low end power.These motors need bigger carbs,the 4 valve head even stock flow way more then the stock carbs do.
As far as price goes you better look at what you get in the carb kits the bp kit comes with everything you need even air box kit.Some of the cheaper kits dont have intakes,air box kit filter and adaptors, cables and so on.Time you buy all that you might spend more money.
 

·
Registered
Joined
·
38 Posts
Discussion Starter #8 (Edited)
thx mates


these are answers helping me out


the thing on those tm-mikunis is:


they fit on the original inlet rubbers up until 40mm carbs...the stock manifolds are overworked...so no need to buy new ones

and at the other end of the carbs i have velocity stacks made of aluminium which replace those stock rubbersxxt between carb and airbox...diameter is 55mm with the TM 40 carbs...so thats the same like at the stock cvk´s...a must is, to keep the original airbox...u can´t take a ride without airbox here unless having trouble with law

the attachment for the throttle cables can be built in the middle of both carbs so that the stock throttle cable fits, too...thats no problem...


i believe your experiences with the hsr´s ... but 1350,-eu is just a number too big...i think i´ll try those TM 40´s and let ya know what they are like when i have installed


cheers


twinfan


ps: igniter-mod is at the end of it all :D
 

·
Registered
Joined
·
1,995 Posts
Just remember that while your goal is more power/torque...a bigger carb will provide more of both. I'm certain the HSR's could be setup to fit and airbox inlet.


Also..while the 36's are the most cost effective they are essentially gaining you nothing except maybe..just maybe a little in the upper rpm ranges.


If you go for the 40's let us know how you make out..
 

·
Registered
Joined
·
38 Posts
Discussion Starter #12 (Edited)
well...the thing is to keep almost the original look...nobody can see 904 & headwork...evenmore we have to go to - let´s say - "check up" all 2 years by a institute which is called "TÜV"...there you get a certificate for the next 2 years...as i don´t want to rebuild all 2 years the airbox to fullfill those "check-up standards" to noise and all the other discriminations, the airbox has to stay where it is...

when u get controlled by police here and they see there is no airbox you get in trouble because of noise-limits with newer models as it simply isn´t allowed for those...

old bikes have more possibilities to noise and even driving without airbox - just velocity stacks on carbs ain´t a problem...but then u got a bike round about 1980 downwards...
as i want to ride and not just work on the bike mine is a newer one

lucky u in US :rolleyes:


one more question:

as i just build up my scram with 904 and headwork at the moment - just waiting for the head to come...can anybody tell me a good setup for the cvk´s with that constellation? restrictorplate and snorkle is anywhere in the garage...my cvk´s have a 128 mainjet and 1shim under the needle at the moment...there is a ZARD 2-1 roadster exhaust on my babe

evenmore i ask because with these datas i can tell the dealer from those TM-carbs, so that he can make a good pre-setup

he´s the guy for mikuni carbs in germany...main importer and really known + good

cheers


twinfan
 

·
Registered
Joined
·
8,872 Posts
I wish i could help you ,you got kinda a crazy setup there.these motors with stock carbs stock heads want more air flow then the stock air box will let it have.Sounds like you are doing some head work and that will make it want more air.A 904 needs even more air flow then stock carbs can flow.I am scared you will end up with a set up that will be like running the choke part way on.I ran into that with pod filters that wouldnt flow enough to keep up .You might can play around and run it on the lean side and get it to run ok at low rpms.But it will be dead meat on top.What pipes are you going to run?
I think if i wanted to do what you want to do I would get someone ral good on a flow bench to flow the head through the carb with the air box and see whats the best he can do to match the head to flow what that setup will flow.904s make there best power up in the rpm range.If you want low end power you might of been better with a stroker crank.They make way more ft/lbs down low you might could feed one at low rpms with your set-up.
 

·
Registered
Joined
·
38 Posts
Discussion Starter #16
Nice lookin bike..I'm going to guess you'll need somewhere between a 145 and a 155 main with a 42 pilot..possibly a shim or 2 on the needles depending on how well you can get this thing to breathe through the airbox.


Where are you?

ähhhhhm...that ain´t mine...that was just a link from the forum


but ok ok...if you wanna see...here u got it:



i love it in that colour...not always that dark and bad style...that pic is an older one...now there is just a lucas-style backlight at the rear fender

and if u want...listen to the beat:

http://de.youtube.com/watch?v=B1ztL1m2T5Y

got more of that crap under my youtubeaccount



cheers


twinfan
 

·
Moderator
Joined
·
29,948 Posts
If the airbox isn't coming off, is there any point even doing the 904 kit or changing the carbs? Now that I have had a look inside the airbox and can see why it is so restrcitive - really if it stays on, no point messing with anything else, except maybe silencers, but that would be more for sound than performance. (You can get a couple of HP I guess but that seems to be about it).

It's pretty easy to take the airbox out without cutting it - seems to me if you're desperate to get more oomph you need to do like Mikeinva says, and then go straight to the big carbs no messing.
 
1 - 20 of 47 Posts
Top