Ignition advance experiments, anyone?

[randy]

Hi, everybody.

Been doing A LOT of riding lately, commuting to work on Swamp Thing. She runs great, 42MPG city, except that the horses only wake up after 3K. From the posts here, that seems to be common for the E and F models. Mine is an F.

So, to get to my point, has anyone tried to remedy the under-3K sleepiness by knocking the advanced ahead a few degrees? I'm running bone stock everything on Ignition and Carbs. What say you?

Just wondering as I bench race here from my desk at the orifice.

If I"m working I'm thinking about riding. If I'm riding I'm not thinking about working.

Cheers,

Randy

[skids]

You can get better low-end torque results by switching to a 4-to-1 header. However, I think that when you get earlier torque and a flatter torque vs rpm curve, you can diminish torque in the higher rpm somewhat. I know this wasn't an answer to your question, but you are looking for more low end torque.

[randy]

Thanks, Skids.

I've got a MAC 4-into-2, other than that it's stock, even the stock ign advance setting.

I've adjusted the pilots over the past week and I'm pretty sure I've got the sweet spot there, so the only adjustment left is the ign advance.

It's raining cats and dogs here in NYC right now, so I won't be able to try new advance settings until next week.

You know, I always prefer checking with the group before attempting any changes. Saves a lot of aggravation.

Randy

[TopCatGr58]

Hey there Skids,

I was told that we LOOSE low end torque when going to 4-1 vs. the stock 4-2's due to the loss of backpressure thru the better scavenging of the 4-1's, but that they add more to the topend because they do scavenge better so you have less back pressures at the higher rpms when you're engine is trying to push more volume thru the pipes at those rpm's!?!?

With my Indy filters and 4-1 and 3sizes up jets, and little big bore like Randy's, mine also doesn't have a lot down under 3 k, but I hardly ever have a chance to run it that low, usually at 4k, cause I don't like to risk stalling the engine taking off from a stop, so I usuaully rev it a bit as I fan the clutch in, and once I get going, I never lug it below 3.5K. This may have been an unconscious adaptation I developed from riding it when it WAS totally stock, but that's my style!

I thought I read another thread/reply by one of the racing guys, PPG or TurboXS about bumping up the advance a bit, I'll have to search for it!

Randy, did you receive the 81 4RO Ign. box!? I'm sure you've been busy, there's no rush to send it back, was just curious!
T.C.

[randy]

Yes, TopCat. I got the 4RO box. Haven't had a chance to open it, though. Don't worry, I'll take good care of it.

Randy

[TopCatGr58]

Hey Randy,

I found the thread and reply from PGG, and what he said was with the higher comp engines ie. Big Bores, that he found it ran better-not as hot by RETARDING the timing a few degrees, not so much for performance enhancement as for protection of the pistons/rings and engine from overheating!!!

He also said that he ran his 78E about 3 degrees advanced, but it was essentially stock, but still related very little oomph below the 3K threshold!?

I'm happy with mine and the power range where it is, so I don't think I'll be changing it!!!! YMMV!!
T.C.

[skids]

I never had the Beast dyno'ed but it has an older Jardine 4-1 on it and it has plenty of torque well below 3000 rpms. Actually, it pulls hard in the upper rpms also. I have seen claims in Cycleworld that show torque curves and they typically show what I was talking about. I am sure that that actual performance characteristics are bike-model-specific. The scavenging thing is a reflective echo type thing I believe.

Originally posted by TopCatGr58
Hey there Skids,
I was told that we LOOSE low end torque when going to 4-1 vs. the stock 4-2's due to the loss of backpressure thru the better scavenging of the 4-1's, but that they add more to the topend because they do scavenge better so you have less back pressures at the higher rpms when you're engine is trying to push more volume thru the pipes at those rpm's!?!?
T.C.

[Dennyz]

My '79F has the Jardine 4:1 and tons of low end. I experimented with advancing the timing and found it not to be of any benifit. All I noticed was my fuel economy dropped. If the initial timing is advanced the centrifgul advance needs to be limited so as not to produce to much total advance (36 deg. BTDC). I found for the weight of the bike, the compression ratio, and type of carbs, the ol' boys at Yamaha got it right.

It has been my experience that messing around with then intake (air box), exhaust system, and carb jetting is where more more can be found.

current setup:

drilled airbox with factory replacement K&N filter
float bowls at stock setting
pilot jets at 45.0 (42.5 stock)
main jets as 145.0 (37.5 stock)
Jardine 4:1 header with R1 stock can muffler

note: valves set correctly, carbs sync'ed and colour tuned correctly.

Motor strong from 2K RPM up to red-line. Second gear wheelie (few inches) typical, first gear wheelie on occation. Motor is otherwise stock with 85K miles on it.

[pgg]

Well, a camgrind - building up the lobes for more lift is gonna give some extra low grunt - more noticable on our 2-valvers than on better breathing 4-valvers. Even though 2-valvers are generally more torquey than 4-valvers. Everything is a compromise though - ying and yang right? Still, a really well designed custom 4-1 gives an impressive boost right across the range on an old XS1100. Mainly mid and high though.

The extra cam duration and overlap on 78-79's cause the 'spongy' 1000 - 3000 effect - inlet and outlet valves momentarily open in unison giving a blowback effect until the cams come on at 3000. Grind back the duration - more low torque but loss of top-end. Increase lift and duration you're gonna have to alter the valvetrain to accomadate. Anyways, a high revving 78 'feels' faster to ride.

[uk1.1s]

Cams make a difference

As pgg says - a different cam profile will make a difference to the torque. One of the things I've seen about the bike I have (Euro spec 1.1 Sport) is that it has a slightly different cam profile to most other XS11's, amounting to the same horse-power output but giving max torque lower down (I think 1000rpm lower I read somewhere).

I can't believe that the land of the rising sun shone on Europe only for a limited engine run to power some odd options, so contemporary bikes with the Euro Sport (mines an '82) may have the same profiles (just thinking about availability for you North American guys). I know that the Austrialian "RH" is pretty much the "Sport" down-under, so I guess that they also have this cam profile. My assumption is (and it's only a guess) that the Midnight Special has the same cam. There may be some out there who will know for sure.

I have the Yamaha factory suppliment for the Euro 1.1 Sport - which includes the cam profile details if anyone is really interested. I sent this to Rockjok at the begining of the year, so if he's had any time to update his wonderful CD-ROM archive of the manuals it may be in there somewhere if anyone has a recent version.

Phew....I'm all teched out!

[chevy45412001]

hot cams

I posted about this in a different thread.The cams in our bikes are actualy pretty hot ,even by todays standards.Call me crazy but a GOOD head job will do serious justice to wake up our motors.Along with bigger carbs.unrestricted air intake,and a 4-1 exhaust.Just remember you have to take it in and get it out to make power(air,fuel-spent gases)

[skids]

Re: hot cams

I don't think you are crazy at all!!! It always works for me. =8-)

Originally posted by chevy45412001
Call me crazy but a GOOD head job will do serious justice to wake up our motors. (snip) Just remember you have to take it in and get it out to make power

[uk1.1s]

Perking it up...

.....no rude sniggers at the back of the class!

Spoke to a guy here a few years ago in the UK who used to drag race a xs1100.

His secret receipe for a good power curve - with a useful puchy midrange was to use Yam FZR carbs with differerent carb intake rubbers to fit on the 1100 head (he never did tell be what rubbers he used) and rejet to 140.

Same guy fitted a Yam Virago 535 rear drive splines and wheel (yes a wire wheel) to the back end to radically change the gearing.

[Shuriken]

LOLOLOL......

[Geezer]

Originally posted by Dennyz


current setup:

drilled airbox with factory replacement K&N filter
float bowls at stock setting
pilot jets at 45.0 (42.5 stock)
main jets as 145.0 (37.5 stock)
Jardine 4:1 header with R1 stock can muffler

From the pic I took of your bike I can't tell if you have an oil cooler on not. Do you have oil filter clearance problems with your 4 into 1 header? I’m looking to install my oil cooler soon and the next mod I have planned is a 4 into 1 header.

Geezer