I Need Help : V-Twin Forum: Harley Davidson Forums

Okla.Dave · 09-28-2009, 04:40 PM

I need help

I had my bike dyno’ed this weekend. My bike is a 2004 fxst with the following:

95”, Twin Cam
Modified Heads from Patrick racing, stage II 1.940 intake 1.625 exhaust with compression releases,

Dtt ignition set at 5, 8.
Ccp is 181 ,
Cam is Andrews 37g.
Pipes are Fat Cats with performance baffle. ( I also have quite baffles, but not dyno’ed )
Carb. is cv40 with 48, 195 jets.

The numbers were not what I was expecting. I was told my clutch was slipping which would explain the low numbers. Your thought and ideas on what I should do to improve the performance. What clutch, carb. change what ever….

If this chart is not readable it reads 83.06 H.P. 93.77 Torque
http://http://www.v-twinforum.com/fo...1&d=1254169919

1949shoebox · 09-28-2009, 06:22 PM

you can adjust your clutch. pretty easy ... check fluid level if too high clutch will slip. also what fluid are you using? that can affect clutch operation as well.

aka_matt · 09-28-2009, 08:57 PM

i think the compression may be a bit low, the 181ccp would put it around 9.5?
can't tell for sure tho til the clutch is fixed...

Okla.Dave · 09-28-2009, 09:12 PM

primary I use Hd Formula +

Rechecked ccp
ccp 192

I used Big Boyz calulator at Altitude Correction 700 feet it show ccp at 192

which would be 10.11:1

Corrected Compression 9.37:1

Okla.Dave · 10-02-2009, 05:03 PM

I adjusted the clutch, put on quite baffle, check ccp.
Had a new dyno run today. The results is better on torque 112ft@2467rpm.
The H.P. is still down but better 88.0Hp@5294rpm.

I think I need more carb. I’ll try a Mikuni 42mm that should bring it up some.

Pikeslayer · 10-02-2009, 05:13 PM

112 ft lbs out of a 95" is about as good as you're going to get.

Okla.Dave · 10-02-2009, 05:27 PM

http://http://www.v-twinforum.com/fo...1&d=1254518802

route66paul · 10-02-2009, 06:03 PM

I got 90/95 with CCP of 160. I had the set of heads done as a street port, but did not CC them. The bike ran strong, better than some that claimed 100/100. You have either:
1. tuning problem
2. porting problem
3. exhaust problem

You may have a sumping problem, or your clutch is slipping badly(I doubt it is that bad)

a 37 build with a carb should really not be above 9.5:1. the tuning can not be presise enough to get past the pinging that will occur.

Okla.Dave · 10-02-2009, 08:35 PM

I must have the timing just right because I have over 3000 miles on this build.
That and a 030 head gasket. No ping. Go figure.

BVBOB · 10-02-2009, 11:32 PM

The improvement is quite dramatic, the quiet baffles brought the torque curve over to the left a bunch, must be very noticeable sotp. I wouldn't be too concerned with the hp number, with torque like that you just shift a little earlier. Also keep in mind the DIN correction will always read a tad higher than the sae correction.

Hillside · 10-03-2009, 07:27 AM

By rights, the hp should be up to more than 88 hp.
Many things could be causing that, but I bet it ain't the carb.

Scott

MaineUltraClassic · 10-03-2009, 10:23 AM

Different dynos were used from the first run to the second run...........that explains the difference in numbers. All dynos are different and will show different numbers.

Steve

route66paul · 10-03-2009, 01:02 PM

but 88hp is a little low. There is a problem at top rpm and full throttle. It could be fuel, but if it was tuned properly, you could still be sumping a little. With that torque, it shouldn't have any problems getting around. torque win races, hp is just bragging rights.

Okla.Dave · 10-03-2009, 01:34 PM

I agree with you Hillside.
I just don’t know what it is. I‘ve read the saying Hd motors are just an air pump. With that, I think backwards the pipes are D&D Fat Cats with quite baffle, that is good, heads are from a well-known builder that should be good, 95” bore Ccp was good @192.
Carburetor and ignition timing is last.
The timing is at lest ok I have no ping.
First tuner said timing was good second said the same thing but would custom tune my Dtt ignition which could net 1 or 2 H.P. most from top end rpm’s, but only after I settle on what I will do about a carburetor.

The carburetor is my next area of learning I have been reading all over the different web
Sites about differences that people have on this subject. If someone that knows about carburetors hopefully a builder could give me good advice as what I could do to up H.P.
It would be of great help and would stop my reading of all the different ideas people have.
I will be riding from 400ft to near 14,000 at times if that is a factor. I’m not a racer but I do want my motor to do what It should do. I also I’m doing more 2 up riding now
(Semi retired). Thanks in advance to any builder that can help with advice.

Dave

route66paul · 10-03-2009, 02:13 PM

The carb and intake can be tricked out to have a better flow. I know after my throttle body was done, it made a huge difference, this was just boring out the stock unit. Get someone that knows what they are doing as opposed to using some stupid kit that is supposed to hot rod the carb.