Heritage top end rebuild / another question

[tinkerman]

Good Day Folks,

Looking at the heads for my 88 evo. The HD Shop Manual says the exhaust valves should be sooty black??? When running this bike the rear exhaust and rear spark plug always ran a bit richer (cooler?) than the front or so I thought because the plug and exhaust would always be on the black side. I thought perhaps I was overusing the choke but it didn't cause any issues so I continued to run it as it was. I have always noticed a slight hesitation off idle when grabbing a quick handful of throttle, even to the point where I would get the odd backfire. Figured the carb (S&S Super E) needed some tuning so I started by rebuilding the accelerator pump last season. That didn't change a thing so I figured I would start playing with the jets this year and get some input from this site.

However as you can see from the photo (I hope) the heads both seem to be running on the hot side of optimal (a little on the white side of tan). Looking for opinions on how hot this cylinder (front) is running based on the photo. The rear one is exactly the same color. I put the plug there so you can compare the color of the insulator to that of the valve.

Not sure if this will even work with a posted photo but my impression is that the bike is running a little lean and I had thought that I would have to lean it out even more to get the off idle hesitation cured. ( Just my theory going in)

Anyway if anyone wants to offer their opinion it would be appreciated.

Thanks,

Tink

[attachment removed after 60 days by system]

[choseneasy]

What jets are you running?

[tinkerman]

Hey Choseneasy

The bike is running a 295 intermediate and 70 main at the moment.

Most of my carb experience has been small engine so if I couldn't fix it with the low rpm or high rpm screws or the float level then I just rebuilt the carb. Now my feeling that with these S&S carbs the principles have to be the same but it will take me some experimenting with different jet sizes to get it right. I am also under the impression that a little lag of idle is common with this style of carb. Not sure what is acceptable but the lag I have experienced has been more "something I have to take a look at" rather than a huge problem. I have kept an eye on the plugs to ensure I haven't been running to hot but now that I look at the heads it seems a little lean for what is basically a pretty relaxed set up. (Dyna single fire, Super E, EV 27 cam, and the stock pipes with a 5/8 hole drilled through the end of the baffle.)

I have downloaded a set of instructions to set up the S&S carbs so it will likley go hand in hand with the top end rebuild. I like rebuilding one thing at a time so I can get a better feel for what improvements/problems are affected by what work if you know what I mean.

Right now just looking for more experienced opinions on how hot those exhaust valves have gotten based on the color. Will pull the valves and check/replace valve guides if nessesary and put in new valve seals just cause I am in there. I was pretty certain I could hear some valve train noise developing over the past season and I had the leaky base gasget thing going on so with 40,000+miles on the top end I figured it was time for a snoop around. Can't really see any issues although I guess one of the lifters could be weak.

As long as I have your ear here, what are your feelings on the value of roller rockers for this engine as I described it. The standard rockers have been doing the job and the engine is just for putting around but if there was any significant advantage I might consider putting in a set.

OK, enough lollygagging, this is turning in to a book.

Look forward to your opinion,

Tink

[ST40]

I'm running a S&S Super E for the first time on my Shovel and having a similar hesitation off idle.  I'm looking into changing jets also, but have been able to improve both lean and rich conditions by a slight carb adjustment.  Sounds like you might be able to open the adjusting screw slightly to improve acceleration off idle.  I never worried about dyno's or things like that before, but I think I will try one along with an exhaust test to see if I am running lean or rich before changing jets.  Good luck!           Marty

[tinkerman]

Right on ST40,

I have played with the mixture screws and the booster pump adjustment and rebuilt the booster last year but nothing seems to make it any better. I have made it worse a few times and had to start over at the original settings. I think the next move after the top end rebuild is to play with the jets. I gues the first thing I will try, knowing nothing about the carbs is try one size larger and smaller in the intermediate jet.

Right now I will focus on the top end rebuild and then when she is ticking over Ok will play with the carb.

Tink

[choseneasy]

  I wouldn't say you are running to lean by the look of the photo.  The hesitation is from a lean transition from idle to intermediate. Some say the 29.5 is too big and has to be sized this way to try to stop the hesitation. Doug Coffee from Head-quarters had a fix for this and allowed you to go to a smaller jet.
  As far as roller-rockers, I would not bother- not necessary with the cam you are running.
If I was to replace anything it would be the lifters with Harley's 18523-86b and a new cam bearing.

[tinkerman]

OK Choseneasy,

Appreciate the feedback. The cam bearing and B lifters are on the parts list for the rebuild along with the later style cyl. studs.

As for the off idle hesitation, you'd think between the booster pump, idle screw and intermediate jet there would be some way to adjust this lag out of the system but the reading I have done indicates that a little hesitation is part of the deal. that problebly won't stop me from trying to tune it out though, but it is a detail/patience thing. Try a different jet, and a bunch of adjustments and if that doesn't work try a different jet and start over. PITA. Otherwise go with a different style carb. It's not that big a deal, but when you are doing slow speed manouvering and you want a little shot of juice to pick the bike up it's not always there right when you want it. You can work around it like a quirk on any rig.

Maybe I'll just idle her up to 1800 or so. LOL

Thanks for the info,

Tink

[Buddy WMC]

It is also quite common for many engines to have too much of an accelerator pump shot. Once you get back together, set the carb with the pump shut off per the S&S instructions and then open the pump up accordingly. Either that, or stop guessing and get the bike to a reputable Dyno shop. That was the best money I ever spent in terms of the difference before and after the Dyno session.

[tinkerman]

Hmmm,

I never thought about the possibility of actually flooding the engine off idle with the booster pump. Will give that a try but I think somewhere in there, there is a gap between the idle circuit, the shot from the accelerator pump and when the intermediate jet picks up the job of fuel delivery. For sure there are tuning guys around that have this figured out.

As for me getting this old evo up on a dyno. Not a bad idea but I have always been a by the seat of my pants mechanical type and these engines are of an old enough technology that I should be able to get it running OK with my tool box. (Hell, it was running OK before the tear down, I just want it running perfectly).

The other issue is that I live way out in the boonies and there may be a Dyno somewhere within half a days run from here but if there is I haven't heard about it. More than likely I would have to hit the ferry and get off the rock..... we are talking a two or three day process here.

Nope, I am just gonna have to rely on what I have in the shop, my eyes, ears and nose and lots of good advise from HTT.

Take it easy,

Tink

[Buddy WMC]

Tink,
We thought my performance build was close on the initial setup. 28.5 int/72 main with way less of a pump shot, curve #4 on the Dyna 2000 ignition. The bike was responsive and ran well and after 500 miles of break time in she went to the Dyno shop. We performed nine pulls and wound up on curve #2 on the Dyna ignition with a 32 int and 68 main. The bike a 93 FXR is nothing short of being a rocketship. The gas mileage around town kind of sucks, but with the Baker 6 speed installed is rather good on the Interstate. A little hesitation at about 2200 rpm turned out to be advance/Voes related as wfolarry pointed out to me. We are working on adjusting the Voes now to not cut the advance back too quickly.

[tinkerman]

Hey Buddy,
Oh Man, my tiny little mind is going into overload.... so many combinations, so much trial and error and right now the carb is zip tied to the front crash bars inside a shop rag and the top end is all laid out on the shop bench.

For sure the dyno takes a lot of guess work out of it and then nails the optimal set up. Guess I am going to have to get the top end back together before the snow melts and then take a handful of jets, wrenches and screw drivers and a note pad and start heading towards our provincial capital. If I haven't got her running smoothly by that time, and haven't got a valve melted on to the head I will likley be gone nuts and can just pull up in front of the sanitorium and check myself in.

Appreciate the input though. For sure the dyno is the way to go but I am so far out in the boonies I have to pack a lunch to take out the trash. Just gonna have to do it by trial and error and hope for the best.

Hey, maybe a buisness opportunity for someone on the rock....how much does it cost to put a dyno in service shop. Of course then you need the tuning experience to use it.

Food for thought though,

Takes it easy,

Tink