Passing Gear?

[Roncoach70]

OK Motoman, I know your itching to solve a problem. I got my SF up and running great thanks to all you guys. Now that I've got 300 miles on her I'm starting to build confidence that she's going to get me home. So tonight I started letting it Rev out. Even stock it's stupid fast 100 in 3rd. OK I noticed that when it gets up to about 8 grand it feels like a car with an automatic transmission shift down into passing gear and just flies. Main jet issue? Thanks for the help.

[TopCatGr58]

Hey Ron,

I'm going to jump in here before Brant gets to. Have to tell you....STOP taking it up to 8K rpm! Yes, we know the redline is there, but that was when it was NEW with NEW valve springs!!! They are 30 years old now, and at that rpm you are risking floating a valve and banging a piston top with it and trashing your new bike!!!

It's hard to determine exactly what you are saying or describing what's happening with your engine or what you are doing? IF you are saying that it pulls hard up to the 8k point and then stops revving/pulling higher....that's NORMAL for these engines and you really need to stop trying to take it up that HIGH....aim for sustained 7.5 k max, a quick rip in 1st or 2nd to 8 OCCASIONALLY may be okay, but not sustained in the higher gears.

Okay, will let Brant chime in now, either confirm....or bust my balls!

T.C.

PS, if the rpms are just quicly climbing under hard throttle but the bike isn't going any faster, then that could be clutch slip!

[BA80]

I've pegged (at least 10K) my 2H7 engine more than once, not on purpose of course, and it's still going strong.

That being said TC is probably right but I gotta say, that red line is probably a couple grand short of what these over engineered engines are comfortable with.

Just sayin'

[Roncoach70]

Thanks TC. It pulls hard up to 8000 continuously with no sign of letting up, but as usual thanks for the education. I was thinking possibly clutch slip also but the speed increases so I assume the clutch isn't slipping if it's going faster? It is running so damn good I cetainly don't want to hurt it. I can't believe how much I love riding my SF now.

[Roncoach70]

Thanks Greg it was still pulling hard at 8k, but I'm to much of a wus to keep pushing.

[Roncoach70]

I got some rust on my header pipes, original exhaust system. I found on u tube rub the pipes with aluminum foil dipped in distiller water. Surprising how well it worked. Then I found a product called colonel brassey that supposed to be incredible at rust removal on chrome. Anyone ever used it?

[MPittma100]

All Engines

Any engine max rpm is determined by the camshaft. All cam shafts have an operating range. An example is a camshaft that has an operating range of 4500-8500. Within this range is where the engine will make its most power. All other components have to be up to the task. Every dyno result I have witnessed shows the engine making max HP well below the max RPM of the cam. And max torque is at a lower RPM than max HP. Dyno sheets do not lie.

In the example, engines with this camshaft make their highest HP at 6900-7200. Any RPM over that is just a waste. Shifting at or just under the max HP RPM will yield the best performance on all engines.

Keeping the RPM on the 11s under 8500 is just being smart. For those of you who must red line your 35 year old motor frequently, I would recommend adding new valve springs and keeping a few valves in stock.

[Roncoach70]

Ok, Max of 7000 rpm it is thank you.

[MPittma100]

Fyi

Ok, Max of 7000 rpm it is thank you.

FYI, aftermarket springs are available. They set up with about 50 more pounds on the seat at same installed height than the OEM springs. A good choice for redoing a head.

[motoman]

OK Motoman, I know your itching to solve a problem. I got my SF up and running great thanks to all you guys. Now that I've got 300 miles on her I'm starting to build confidence that she's going to get me home. So tonight I started letting it Rev out. Even stock it's stupid fast 100 in 3rd. OK I noticed that when it gets up to about 8 grand it feels like a car with an automatic transmission shift down into passing gear and just flies. Main jet issue? Thanks for the help.

Actually 85mph IS top speed in third gear............on a Standard. The 17in. rear wheel instad of the 16in. on the Special helps that top speed a bit in third. No issue I hear here cept the 100mph in third is BS unless the 850final conversion has been done. Sounds like your speedo is off a bunch. Remove the fuse panel and pull apart the smallest connector and clean shiney those two tiny contacts and plug-in. Do the same with rest of those connectors behind there............. 'just cause' if you don't..

[BA80]

The valves are so light on these engines that valve float is virtually impossible at any RPM these things are capable of without grenadining.

Heavier valve springs would only cause quicker and more heavy valve seat wear. More frequent valve adjustments and even thinner shims.

[Roncoach70]

Thanks folks. Moto just at the fuse panel to look at my speedometer ? I fortunately have a police officer friend that I will also see if he will radar me. Thanks Ron

[mrhammer2u]

I'm experiencing the same thing. I've been advised by some board members here to replace my clutch springs, which is being done now. Sounds like you're clutch is slipping as well.

[trbig]

If you were on a 'Busa, I'd say you were getting a bit of back wheel spin, but since we're talking under 100hp here... I'll throw my "It's tired 30 year old clutch springs" in there also. Is it possible you have a bit of a stumble and it finally starts hitting on all cylinders and feels like a passing gear? As smooth as these inline fours run, sometimes it's hard to tell when only three are hitting. Then when the 4th starts in, you feel the extra power.

Can't confirm or deny the 85mph limit in 3rd with stock final drive. That just SEEMS a little slow to me? I've been wrong lots of times though. With the final drive mod, it only changes the rpm at 70mph in 5th by 7-800 rpm and I can easily hit 100 in 3rd with lots of room before redline. (According to GPS, not stock speedo.. which only goes to 85 anyway. lol) The 17" rear tire gains you 3-400 rpm if I remember right.

Anyway, Barnett Springs. They're your friend. Until you're stuck in traffic. lol.

[Roncoach70]

Thanks everyone looks like I'm in the market for clutch springs and might as well get friction plates while I'm at it. Is this similar to doing my bike clutch jobs or much different?