Triumphrat

sbpark · 11-15-2009, 08:25 PM

so far i am loving the bike and the carbs and cams. (still have stock 865 motor with ported and polished stock head, UNI filters on the FCR's and soon to be installed Pieman ignitor). i just have a few questions for others on here who have had the carbs on their bikes longer than me.

any quirks or points of interest you've noticed since installing them? any hints, advice or words of wisdom you've come across along the way since installing them? how many of you ended up staying with the jetting that the carbs were shipped with when you originally purchased them and how many of you ended up tweaking them? (i can tweak the snot out of the CVK's since they are very basic but the FCR's are a bit intimidating, but i feel compelled to learn how to tweak and tune these cabs when i eventually get an AF gauge).

obviously you have to roll the throttle to get going from a stop which is no problem, and one thing i have to remember too, is to down shift if i am just cruising in traffic, because if you are at low RPM's and try and twist the throttle it bogs down. the bike loves to rev now and feels like it doesnt want to stop pulling all the way up to redline, and is a blast on the freeway and overtakes other vehicles with much more confidence than previously and pulls more coming out of turns.

cold starting is a bit of an issue for me. was in the high 50's maybe low 60's here the other morning. i did what was recommended; 3 quick twists of the throttle then fire it up. the bike wont hold idle and will backfire (from being too lean i am guessing?) and die. the solution i have found was to crank up the idle adjust knob when cold, fire up the bike, and as the bike warms up/as i am riding it adjust the idle back down to about 1100-1200rpm. i was also told overtime i will get better at starting up the bike and wont have to crank the idle (which is something i dont want to do and waste fuel and run super-rich whenever i cold start) i'll be able to find a sweet spot where i just barely twist the throttle to keep the RPM's up a bit and after maybe 30 seconds it will idle on it's own.

my bike has always been picky at idle and even with the CVK's would backfire occasionally if the idle mixture was too rich or lean. once the bike is totally warmed up it runs really well and no backfiring. i do get a lot of popping on over run/deceleration with the FCR's, but have been told this is normal as well with these carbs (over run popping has to do with the idle mixture, not the main jets). it's more prominent with the FCR's than the CVK's, and the sound/pattern is different. the CVK's popping on decel was more disorganized sounding and pops were further apart, with the FCR's it sort of sounds like quick bursts of machine gun fire if that makes any sense?!

Also, is it safe to say once i put in the Pieman ignitor with the advanced timing it will help with cold starts?

just thought i'd get your thoughts and ideas. thanks!

EDIT: just went outside and cold started the bike for the third time (ambient temp around 60 degrees) and it was much better than the previous two times. still coughs and dies but with just a slight bit of throttle will hold idle. seems like the FCR's take longer to warm up than the CVK's, but have to keep in mind these are racing carbs and also dont have a choke.

sweatmachine · 11-15-2009, 08:51 PM

for real man, as soon as you have the $$$, get an Air/Fuel ratio gauge from Innovate. I would never go back to riding without one.

propforward · 11-15-2009, 09:08 PM

Sweat makes an excellent point - well worth doing th a/f gauge, especially on carburettors as versatile as these. I could not have tuned mine in as well as I have without one.

I have my FCRs set very rich at idle. This helps the cold starting, and also cuts down the popping on the overrun, although a bit of popping is good character! At there slightest opening of the throttle though, the a/f mixture goes right to about 12.7 to 1.

You will get the hang of starting them My bike actually starts easier than it ever did with the CVKs, although sometimes it does take me a few goes to keep it running. I have been starting my FCRs in mid 20 degree weather, and they still fire right up. I do the same as you, turn up the idle a bit until warm. As you say - they are racing carbs so you have to be prepared to fiddle a little.

I don't think the pieman ignitor will help the starts at all.

I have found that once I got mine tweaked a little, the bike will pick up even from very low revs with no problem. I suggest you try lifting the needle a notch and see what it does. Needle height has a massive effect on the FCRs. The needles come into play quickly and actually have an effect all the way through the throttle range. The Main jet also can affect the mixture as low down as 1/8 throttle, but the degree to which these factors have an effect changes over the throttle range.

The setup I have now, is exactly as Carlos shipped the carbs to me, except for the main jet and the needle clip position. That man got them damn close for me.

I do use a different needle in the summer. I personally have no problem with swapping between needles for different seasons to maintain a perfect mixture, because it takles all of 5 minutes to swap them out. Don't even need to take the seat or tank off.

I think with a bit more work I can optimise the needles so that I can just leave the carbs alone between seasons.

Sounds to me like yours are very very close. I bet that bike runs like a scalded dog! Maybe even faster!

One thing on these carburettors, it seems to me that the bike runs best and transitions best on the rich side of things - I would say if you can keep the mixture about 12.7 to 13.0 to 1, it really runs well. I have mine set such that it runs at those settings for acceleration and power, but I lean it out a bit at 1/4 and 3/8 throttle, which are the cruising settings, for a bit better fuel economy. I don't have it perfect yet, but it's pretty good.

mikeinva · 11-15-2009, 11:48 PM

I agree what pro says but I bet it will start better with the pieman box the map he puts in there is way better then the stock 865.I think if you get them dialed in 100%(maybe on a dyno) you will find they run alot better.Atlest you got carlos to help.

mag10 · 11-16-2009, 09:56 AM

are you guys using the TPS with these carbs? I have not plugged it in, as it was long ago removed from the CVKs (started and idled better without it). But I've wondering if there is any value to it now or not.

I agree on the starting comments, 3 twists and she fires right up, 20 - 30 F. Something I have noticed is its far quiter on the over run without so much popping as before (could be the quick bursts sbpark descirbes). In fact the motor seems quiter over all (realitively speaking).

I have not noticed any hestitation or lag thru out the rpm range, it wants to take what ever punch I give it. And way quicker to wind out. I thought that the roll off was a bit slow, but found yesterday that my thottle return cable was a bit slack.

propforward · 11-16-2009, 10:02 AM

I am still using the TPS, though from what others have said, it doesn't matter much if you leave it off. I had the TPS on my FCRs, so I plugged it in to keep everything tidy pretty much.

I really need to get a pieman ignitor. I think that's something I will do over winter as well as cams, all being well. I kind of assumed that the pieman ignitor involved changes to the higher rpm end of things, but I realise that that is an assumption - I don't actually have anything to base my comment about it helping starts off - so if it does help with cold starts that would certainly be great.

Aussiematt · 11-16-2009, 11:06 AM

I've never had an issue with starting with the FCR39's. Last night I went for a ride and it was cool (for SF) - say mid 50's. Four quick twists and she fires up instantly - I hold it at 1500 rpm for a minute or so and then she idles, albeit roughtly until warm then its a smooth idle at 1000-1100 rm. I have the pieman ignitor and have noticed no real difference on start up. However once underway (I have 813 cams) the Thrux certainly runs significantly more smoothly. The bike hates if I close the throttle quickly but I understand that's normal with FCR's. I missed the growl and the overun grumble initially but its feels faster now after adding Pieman - overall the Thrux is more refined in its operation. I have not yet adjusted the carb set up that came with the FCR's as it seems to run so well (especially when the ambient temp drops to around 45-50). I have not been able to find a competent dyno tuner up here in the bay area so I may have to resort to the A/F gauge that Sweat raised. I get about 95 miles on a tank before hitting reserve

PS. I have left on the TPS

HOOPLA · 11-16-2009, 01:02 PM

Hi sbpark,

I've had the FCRs for 2 seasons and the Innovate AF gauge slightly longer. Both are worth the trouble to install and learn how to use them.

My carbs came a long ways from correct when I first got them. The AF gauge helped a great deal to obtain the most from the carbs.

It sounds like your carbs are off on the low end if it's bogging when you roll the throttle on quickly. If responce at mid throttle is good and the top end sounds like it's good, keeps pulling etc, then an adjustment to the fuel screw or air screw may be necesary. These control the low rpm AF ratio and is the biggest difference in the tweaking process from the CVKs.

There has been a lot written on the this forum about tuning them, take the time to review the notes, it was/is very helpful to me.
The AF gauge install has been covered as well, so dig it out.

I strongly suggest you find all of the different areas that can be tweaked on these carbs and write down where each item is set at, or the size of the jet in place. Read the tuning manuel for hints as to what effects a region of the carb. You'll learn that changing anything has an effect elsewhere in the AF ratio.

You have to lift your tank up to get at the needles, remove the fuel line to give you some freedom and just lift and slide the tank backwards onto the frame, yes the seat must come off too,

Learn where the fuel pump rod is, as it will come out of its working area and need to be reinserted after dropping the carb bowls.

A good mirror is also very helpful in seeing the undersides of the carbs, along with a light that can be held in your mouth when you need to use your hands..

So while you're learning the locations and setting of everything, order up the Innovate AF gauge. This was for me a 2 day project, exhaust pipe needs to come off to weld in the test bung, then the wiring, instructions were great, just take your time.

Hope this helps a little,

Hoopla

B02S4 · 11-16-2009, 01:15 PM

Quote:

Originally Posted by propforward

...The needles come into play quickly and actually have an effect all the way through the throttle range. ...

FWIW, I have found this to be pretty much true with CVK's also.

I want FCR's. Bad.

propforward · 11-16-2009, 09:18 PM

Very good advice from Hoopla there. I put together a spreadsheet to track all the changes I was making, and what I felt about the results, as well as a/f readings. It is well worth taking the time to do it that way - it helps a lot later on.

B02S4 - yes indeed, quite so.