Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[103RKyeehah]

Ok, guys, I bought an 03 SERK.  Previous owner dropped in a set of 257 cams, thunderheader 2-1 exhaust, pwr cmdr, and 6speed tranny.  Overall, I'm happy with the bike. Here's my problem, having jumped off an 88" RKC with no major motor upgrades, I'm not sure if I'm getting the most out of this thing.  I haven't dyno'd it yet.  Runs rough when motor's cold, lurches in 3rd at around 2k rpms, runs like a baoh in any gear from 3200rpms and up.  I was told the 257 cams were a little tall for cruising around 2500 to 3000rpms.  Im running 2450 at 72mph in 6th. 3100 in 5th and all I have to do is open her up and hold on.  Just not happy with the around town performance running between 2200 and 3200rpms.  Any suggestions?  Any way to tune this up w/o major work?  What about a different cam?  Thanks.

[Unbalanced]

103RK,

Some of the higher lift cams dont run that well down low like your seeing.   Do you know if any head work has been done to the bike yet?

Check for any leaks around the intake can do this yourself with brakeclean
Check for any exhaust leaks even minor ones around the heads / fitting areas
What I would do is have a compression test done.
Dyno the bike to be sure the Air Fuel is correct

After double checking the dyno and knowing what your compression is make decisions or ask then what some people here might suggest to you.

You have a few to many unknowns to make a good decision in my opinion until these questions are answered.  

[103RKyeehah]

Thanks, I haven't done any of that yet.  I am burning more oil than I like.  Some guy told me though, if you weren't burning a little, you weren't getting the most out of your motor.  Bike came from GA where temps run a bit warmer.  Could dynoing it work out some bugs?

[Unbalanced]

RK103 your going to burn some oil its just the way it is.   If your buring more than a quart before your 2500 miles services it is an issue and should be looked into.

What you have is a high lift cam it runs best balls to the wall upper end ie FAST.
Dynoing the bike may take care of some air fuel mixture problems / timing and can be done and may eliminate some of your issue.

Why i suggested the things I did is to be sure you dont have some other compounded problem that your not aware of and then you would be wasting your money getting a dyno tune done because when you finally found the leak it would change the way the motor runs.

My suggestion if all checks out A ok and you still dont like the way the bike is running is to either try the 251 cam I had it in my 103 that built up from 88 to 95 to 103 and i loved it and ran it with a baker six speed or to go to a gear drive cam such as the 55g from andrews, but still you need to know your compression rates to decide what cam will work best if you are unhappy with the one you have.   You do not want to put a fast closing cam that runs from lets say 9.5 to 10.2 compression and you have 10.5 to 1 compression it will detonate and ping like a bear on you.    

I still stand on my initial recommendations to you before you go blowing money that maybe wasted.

[BLM777]

Got to agree with "Unbalanced" on the 251 cam.

[103RKyeehah]

UnBal, thanks for your suggestions.  Sounds like I have some work ahead of me to fine tune this thing.  I hope to get this to a local speed shop and have them dyno it soon.  What can you tell me about burning oil.  I've put just over 2200 miles on the bike since I bought it and have added about 2.5 quarts of Syn3 to it.  I have no obvious leaks on the outside.  What else should I be looking for?  Thanks

[DCFIREMANN]

I think you do have a problem and it might be in the cylinders. I would do a leak down test of the motor along with a compression test. This will tell you if you have a problem in the cylinders or not. I would pull those cams out of that bike and install a gear driven set of cams. You may have a problem with your power comander that may have caused you to have problems else where IE lean mixture. Do a few simple tests before you go into some major work unless that is what you have in mind already.

Be Safe

THE DAWG

[Unbalanced]

I have a question for you before you read below who did the oil change prior to you having this last one done.   You do know you will need to put in more than 4 quarts of oil right a lot of people do not do this when they have the oil cooler on the bike.   People forget its up there and automatically short you some oil and a lot of the guys run these bikes a bit short to begin with due to overfilling when the oil is cold.   Just something to consider.  Mine is good around 4.5 quarts in that area.   Not saying its the answer but if someone put in 3.5 quarts to be safe and then shorted you some by forgetting your oil cooler that is a quart right there and then if you ride hard you might be within the variances of how much oil is ok to  burn off.   just a thought before you read on.

If you have lost 2.5 quarts in 2500 miles Harley will consider that a problem anything over 1.5 quarts they start to monitor it and then decide how to act it may take you 5k miles once they get involved to warranty it, so I would not jump right in and change the cams.

[GC_Super]

103 RK, I noticed a couple of things in your post. First, your coming of a basically stock 88" motor, which has a lot more torque than a high cammed stroker, and you mention lurching at 2K rpm in 3rd gear. That's lugging the engine and will do damage to the lower end eventually. I think your adjusting to the different motor and need more time to learn how it operates. Granted, the 257 is not a low torque cam, but if you ride it differently, ie;  higher rpms, you might like it a lot more. JMHO, and it's cheaper than a cam swap. Also, a primary chain adjuster like the M6, HB 125 or now HD has one, will eliminate some of that low rpm lurching.  [smiley=xyxthumbs.gif]
Bottom line is that motor was not set up to your particular riding habits.

[Crawdaddy]

Unbalanced is right on.  But I think you could achieve the same performance with the 251 cam if you port the heads and increase the valve size.  The cam is allowing more mixture into the cylinder by lifting the valves higher.  Larger diameter valves can do the same without the vibration.  My partner has a 88 with the 95 upgrade and has the same complaint at 2500 RPM.  Unless he stays in lower gears and runs at 3200 to 3500, he shakes like a naked eskimo.  

Crawdaddy

[Twolanerider]

Unless he stays in lower gears and runs at 3200 to 3500, he shakes like a naked eskimo.

[103RKyeehah]

Thanks for all the advice guys.  I just dropped it off at a local and trusted speed and custom shop.  They'll be running a series of tests to determine where I'm losing oil and possibly compression.  They'll also run a series of dyno runs to fine tune it once any underlying problems are found.  Should be running great when they're done.

I'm getting used to the difference btwn my old 88 and new 103.  Not sure how long I want to cruise around at 3200 and up though.  Switching to the 55g or 251 is something I'm seriously considering.

I've learned to really appreciate what this current setup can do though.  Had her out on the highway for a while today.  Yee haah, she like to run fast.  Got goin' through the gears (btw, no rev limiter at 6100rpms, Unbalanced) and up to cruising aroung 3200 in 5th.  (that's about 80mph).  Just opened her up to triple digits and the power never went away.   [smiley=huepfenjump3.gif]

So if you like the top end and don't mind losing the mid-range, I might have a set of 257s for sale.  
Thanks for all your input.  This is a great forum. [smiley=xyxthumbs.gif]

[Unbalanced]

Sounds like you had a great day.   Hope the prognosis is just as good.   Keep in touch and let me know what they find and you decide to do.

[103RKyeehah]

OK guys, I've had my first check up at the local speed shop I mentioned before.  Didn't get to the oil buring problem yet, but did address the driveability of the bike.  After serveral hours on the dyno and several adjustments to the PC, the bike is running better than before.  Found out it was tuned too lean and that was causing the sputtering at low RPMs and when engin was cold.  Richened it up a bit and things seem much smoother.

Next visit will be to address the oil burning.  Still need to drive it a while to verify consumption is the same.  

I've got a few new questions for the group based on what I've learned so far.  1. Gear compensator- changing out the front pulley to get the torque into the lower RPMS?  2. Front plug white, rear plug black (after recent changes)??  

Oh yeah, you probably want to know the numbers from the dyno.  Nothing really impressive: 116 FP tq and 98 HP. After a very steady arch, both peaked out around 95 MPH which translates to about 4200 RPMs.  

Local guy, been building motors for years, says headwork in in my future and says my TH exhaust is providing  a bit more back pressure than I need for how I ride.

OK sorry for the book, but I could use some input to keep things in perspective.  Thanks

[GC_Super]

116 tq sounds pretty good. Unless you have a huge dip down low, those numbers aren't that bad.  Kinda suprised the 257 produced a lot more tq than hp.  Looks like if you get it all tuned up right, you might be happy.  Oh what did I say?  A harley rider happy without looking for more?  LOL   [smiley=xyxthumbs.gif]