SH775 swap - engine won't rev over 6k

[hotrodalex]

I just swapped my old R/R for a SH775. Now it won't rev over 6k rpm. I'm assuming it's not getting enough voltage for the sparkplugs? Anyone else ever had this problem?

The SH775 is used from ebay. Is it just bad?

 

[fastbysuzuki]

I may be bad, have you got a multimeter to test? If so set it to 20 volt dc setting connect it to the + - on the battery to see what is happening at tick over and 5000rpm and post the readings on here.
are you sure you have the 775 connected correctly? You do not mention what bike you have that would help put the year and model in your signature then every time you post everyone knows what bike you have.

perhaps an explanation of how you have connected it to your bike would help

IMG_2672 by peter wood, on Flickr

 

[Nessism]

R/R problems won't cause the bike to not rev properly unless you are starting off with a dead battery.

Charge battery fully and then check both running and charge voltage.

 

[Steve]

I'll be working in my shop tomorrow, bring it up, we can test it.

.

 

[hotrodalex]

It's a '77 GS550.

The wiring is all stock AFAIK. (I haven't changed anything with the headlight loop) I have the yellow, white/blue, and white/red going into the grey side, then red and black going into the black side.

Can I rev the bike to 5-6k in neutral and get a good voltage reading, or should the bike be under load?

R/R problems won't cause the bike to not rev properly unless you are starting off with a dead battery.

Charge battery fully and then check both running and charge voltage.

It has a brand new Shorai lithium battery. Voltage was around 13.2-13.3. I believe the voltage was the same when running.

Do you think it's more likely that the stator went bad?

 

[posplayr]

It's a '77 GS550.

The wiring is all stock AFAIK. (I haven't changed anything with the headlight loop) I have the yellow, white/blue, and white/red going into the grey side, then red and black going into the black side.

Can I rev the bike to 5-6k in neutral and get a good voltage reading, or should the bike be under load?



It has a brand new Shorai lithium battery. Voltage was around 13.2-13.3. I believe the voltage was the same when running.

Do you think it's more likely that the stator went bad?

When you turn the key on with headlamp and kill switch active you are putting approximately a 10 amp load on the battery. While the Quick test details what to expect for a ;lead-acid battery in step 1 and step 2 , the LiIon should not be too different.

The Quick test is the first step at attempting to diagnose your charging system

 

[Guest]

I'm not sure how a new R/R would stop it from revving up. If the battery has the proper volt 12.6+ it should rev to whatever rpm you want, if the battery is low because the R/R isn't charging it, then it shouldn't be restarting because the starter will be drawing the voltage down each time.

It's hard to speculate without some test numbers from the battery before and after startingd an the stator AC voltage at 5K.

 

[hotrodalex]

I'll do the Quick Test tomorrow and go from there.

 

[Guest]

I'll do the Quick Test tomorrow and go from there.

Make sure your battery is fully charged.

 

[Steve]

Good luck with the Lithium battery. :-k

What was your incentive for switching to a Lithium battery? Weight? Cranking capacity? Money burning a hole in your pocket?
If your incentive was weight reduction, you saved about 5 or 6 pounds. On a 500+ pound bike, it doesn't reall matter that much.
If your incentive was cranking capacity, you might have a small edge.
If you simply had too much money, you found a good way to remove some of it.

I ask these questions and add the "good luck" statement because Lithium batteries require a rather specific charging protocol for proper full charging. Our bikes (and I am assuming you are talking about a bike, even though you did not mention one) are set up for lead acid batteries, which don't require anything special to charge them, just plenty of voltage.

.

 

[hotrodalex]

Finally got around to testing some more.

Bike off: 13.7 volts

Bike idle: 13.2v
2500 rpm: 13.2v
5000 rpm: 13.2v

 

[posplayr]

Finally got around to testing some more.

Bike off: 13.7 volts

Bike idle: 13.2v
2500 rpm: 13.2v
5000 rpm: 13.2v

It would have been nice to see the battery load tests (key ON) and (key OFF after running); you just follow the directions.

Since seems to be too much trouble, you should test Phase B (leg to leg and leg to ground @ 5K) or change the stator.

 

[tom203]

Yes, do the AC stator tests..my last stator behaved like yours- mid 13 volts. Upon removal, one stator winding was cooked.

 

[posplayr]

Yes, do the AC stator tests..my last stator behaved like yours- mid 13 volts. Upon removal, one stator winding was cooked.

View attachment 55766

The question I really have is what is zero charging battery voltage under load? Is it 13.2V? For a Lead Acid , it would be closer to 12.8V.

For this LiIon battery, 13.2V could be either A.) zero charging or B.) partial charging. Only knowing the battery voltage with key on would settle that.

Probably the same outcome, burned stator means Shunt R/R ==> change both.

 

[Steve]

And while you're at it, ditch the Lithium battery. As previously mentioned, they can not be properly charged by an old GS. In fact, that might be the entire problem, not any of the other stuff.

And with all the well-publicized problems with Lithium batteries, are you sure you want one under your butt, right near the fuel tank while riding? :-k

.

 

[posplayr]

And while you're at it, ditch the Lithium battery. As previously mentioned, they can not be properly charged by an old GS. In fact, that might be the entire problem, not any of the other stuff.

And with all the well-publicized problems with Lithium batteries, are you sure you want one under your butt, right near the fuel tank while riding? :-k

.

This document summarizing LiIon battery charging. I suspect any LiIon battery pack designed to be a drop-in replacement for a Lead Acid, must have some type of charging conditioning electronics built in.
Here is an example of voltage and current profiles for charging. A standard R/R is going to put out a fixed 14.5V nominal and the current will be whatever the battery itself controls or (doesn't control to).
Maybe the charging system can't support the current demand and it can't actually get to 14.5 till charged. That is also what happens to Lead Acid which is why you have to charge the battery to get the proper charging test results.

They sell them so they must be OK, that doesn't mean that they will have optima longevity without some internal electronics.

https://www.digikey.com/en/articles...igner-guide-fast-lithium-ion-battery-charging

Figure 2: Li-ion charging profile using constant-current method until battery voltage reaches 4.1 V, followed by ?top-up? using constant-voltage technique. (Image source: Texas Instruments)

 

[Steve]

Thanks, Jim, I have never seen the curve or the actual numbers.

Looking at the 4.1 volt "full charge" number, I would guess that the battery will never get to full charge. If you put three cells in series, the nominal voltage will be about 9 volts, the "full charge" voltage will be 12.3. If you put four cells in series, you would have a nominal 12.4, which is pretty close to what the bike is designed to use, but your "full charge" voltage would be 16.4, which simply ain't gonna happen.

Maybe there is some circuitry to control the charge, maybe there isn't, I don't know. It is also possible that the manufacturers are going on the assumption that we are willing to accept some trade-offs for the 'benefit' of weight reduction. Even a modestly-charged Lithium battery should be better than a poorly-charged lead-acid battery, and I'm guessing that most purchasers are getting a Lithium battery when their lead-acid battery fails, so ANY state of charge on a battery will be better than what they had.

Just guessing. :-k

.

 

[posplayr]

Thanks, Jim, I have never seen the curve or the actual numbers.

Looking at the 4.1 volt "full charge" number, I would guess that the battery will never get to full charge. If you put three cells in series, the nominal voltage will be about 9 volts, the "full charge" voltage will be 12.3. If you put four cells in series, you would have a nominal 12.4, which is pretty close to what the bike is designed to use, but your "full charge" voltage would be 16.4, which simply ain't gonna happen.

Maybe there is some circuitry to control the charge, maybe there isn't, I don't know. It is also possible that the manufacturers are going on the assumption that we are willing to accept some trade-offs for the 'benefit' of weight reduction. Even a modestly-charged Lithium battery should be better than a poorly-charged lead-acid battery, and I'm guessing that most purchasers are getting a Lithium battery when their lead-acid battery fails, so ANY state of charge on a battery will be better than what they had.

Just guessing. :-k

.

Electronics is asymptotically going to zero so don't underestimate the ability to stick some DC to DC converter in to optimize charging. I don't expect every joe blow to do it, but it is certainly economically feasible/possible.

I bought a Lithium Ion batt from one of the top manufacturers (about 7 years ago), and went to all the trouble of cutting my battery box down and the battery went dead in one week from a small current drain and killed a $150-$175 battery. It obvioulsy had no electronics in it to prevent that.

 

[Steve]

Which is pretty much why I watch with amusement all the posters that install them for weight savings. Saving what, 8-10 pounds on a 500+ pound bike? On a race bike, yeah, no problem. ANY weight saving is better performance, but I just don't see any advantage on a street bike.

.

 

[posplayr]

Which is pretty much why I watch with amusement all the posters that install them for weight savings. Saving what, 8-10 pounds on a 500+ pound bike? On a race bike, yeah, no problem. ANY weight saving is better performance, but I just don't see any advantage on a street bike.

.

Hand grip tassles might be more functional? With a dead battery the first week , it would certainly have been the case.