Hard to start high comp!

[Spiff]

Hi, just got my bike back from a service, the mechanic said I should get a new battery since the engine was turning slowly. Funny thing is the battery WAS new!
I mentioned this to the guy who has taken care of the bike for my mum and he said it's always been hard to start on the electric starter, no matter what battery was in there, he said it was because the engine was high comp.
Could this be true?

 

[Steve]

Even new batteries can test poorly, so check it out. Have the battery tested under load (after a full charge, of course) to see what it's actually doing.

Yes, motorcycle engines are relatively high compresssion, especially when compared to most automobiles.
Most of our engines are close to (or just above) 100 horsepower per liter displacement.
Move that direclty to a car and you have some amazing figures.

Since yours is the first one in the last 30 years to have this "problem", I would suspect that something is wrong, possibly your mechanic.

.

 

[Spiff]

I know, but this engine isn't stock. It's got higher comp than standard, at least that's what I've been told.
It really bugs me that I can't get a hold of the previous owner so I can figure out what exactly has been done to the engine. I know it has a 4-1 exhaust, pod filters and a re-jet. Someone on here also said it had CV carbs by the look of it. But thats the stuff you see, It's harder figuring out what's inside the engine.
Or would I find out if I took a compression test on it? I should be higher than the stock values then?

While we're at it, how hard is it to kick-start a stock GS? Do you really have to work it or should it be pretty easy to kick? I have no other GS to compare with so I don't know, but I feel mine is a little bit on the heavy side...

 

[Steve]

If you have CV-type carbs on your bike, then it definitely has had some work done to it.

It will be easy to tell if you do, indeed, have CV-type carbs. Look at the tops of them. Are they rather rectangular, with a dome and held on with three screws or are they round, flat and held on with four screws? The round flat tops are on CV-type carbs.

Higher compression won't necesarily show up in a compression test. Some times, when higher-compression pistons are installed, different cams are also installed. These cams will have different opening and closing times (related to the crankshaft rotation) to take advantage of high-speed operation, so they may bleed a bit of that compression at lower cranking speeds.

How hard to kick-start? Let's just say that a stock, well-tuned GS is easy to kick. In fact, I have used my hand on the kick start lever and started the bike with a modest push.

Have you done all the basic maintainence to ensure that you have a good starting point? Clean carbs are a must. If you have been running the bike regularly, they are probably OK. If the bike has been sitting for several months or does not run well, it's time to clean them and install new o-rings. Valve adjustment is critical. Your valves will tighten with use. Tight valves (especially the intakes) will make it hard to start a cold engine. Ignition timing is also important. Your bike came with points to trigger the coils. If they are still in use, make sure they are clean and properly adjusted.

.

 

[Spiff]

looks flat and round to me?

I don't think you would be able to kick start this GS with your hand, but maybe it's not properly tuned as you said

The bike has been sitting for a very long time. So I had it serviced just now, valve adjustment and also to resync and tune the carbs. Don't know if he cleaned them though.
Bike runs great I must say.

I went down to where it's stored to check out the battery but that's fine, 12.8V,
I also tried to start it a few times.
Sometimes it spins around slowly, but most time it spins around like it should.
Here's a "slow" start:
http://s2.photobucket.com/albums/y41/nexxuz/GS750/?action=view&current=VIDEO0014.mp4

Then another try, fires up imediatly...
http://s2.photobucket.com/albums/y41/nexxuz/GS750/?action=view&current=VIDEO0016.mp4

So I don't know how concerned I should be, 'cause most of the times I tried to start her up it's fine.

 

[elrico]

Bike was sitting for long time. Hope no fuel leaked into engine crankcase oil over time sitting,or was fuel/tank empty? Too high level of just/oil or if water,gas somehow entered, now added to oil level will create much internal resistance,elect.start even w/perfect batt.will struggle mightily,kickstart will also be much harder.Was oil level checked to be correct and viscosity# as well,oil filter correct/proper spec and installed, and oil pressure at expected range?

 

[Steve]

looks flat and round to me?
...

Yep, "flat and round" for sure. Those are definitely CV-type carbs.

I will have to wait until after work to check out your videos.

.

 

[streetfighters]

I'm no expert by any means, but:
Just to check this off of the list,verify and maybe clean up the engine ground and cables from the starter to solenoid etc. Nice 'n' shiny is good, dull and dark is bad. You are in Scandinavia, right? Cool and frequently damp I'll bet. I would think the compression would need to fairly high to impact starter rotational speed.

 

[salty_monk]

I would bet on high resistance in the system somewhere... maybe even internally in the starter worst case.

Best case is a load of dirty connectors or an overheated cable.

 

[Spiff]

Oil/filter was changed before I first started it up.

Yeah, cleaning the bike, including the electrical system is on my to-do list for this winter.
The front brake switch doesn't work either, along with some other electrical gremlins :/

 

[49er]

You probably do have a high comp engine. Easy to check, just warm the engine and check compression with the throttle wide open. Stock GS pressures range from 155 - 175 psi. If yours is around 190-200psi, that's the cause of the reluctant cold starting. You can help the situation by using a battery tender and having up to 13.7 volts available just before the initial start.

I get the very same results when I start my 10.5-1 GS850 for the first time after it has sat for a few days. Once the engine has been run, all restarts are free spinning. I believe any voltage lower than 13 volts doesn't give enough punch to spin against the higher than stock compression. I know in my case that I don't have any suspect electrical connections contributing to this problem.

By using an AGM battery and for longer breaks a tender, you'll notice a big improvement.

Your engine will be fitted with an '80 onward GS850 head to accommodate those CV carbs.

 

[Spiff]

Thanks, lots of tips here. I'll be sure to check them out

 

[Normk]

By the sound you have a starting system issue rather than engine mechanical. Begin with connection cleaning- don't just assume, actually clean the connections to bright color. Shiny black is oxide so not good.

Check voltage drop across the starter relay. Place positive voltmeter lead onto the battery cable side of the starter relay and negative onto the starter cable side. Crank the engine and note the voltage during cranking. Voltage should be 0.2 volts or less.

If you indicate more than 0.2 volts the relay needs cleaning or replacement.

I am assuming that you have a known good battery which has been tested in another bike? Bike batteries are wierd things which act up in ways never seen in automobiles so the best way for a home shop is to try the battery in a similar sized bike and the other battery on this one. A battery having low capacity will cause high starter current (this is not an Ohm's Law problem) which can be difficult to attribute to either battery, starter or engine effort. Always verify the battery.

Haven't had one of these starters apart or not for so long as can't recall but many of the small Japanese starters (starter = electric starting motor) use an "O" shaped brush holder disk which grounds the ground brush to the starter field housing and end cap because the brush holder is clamped between the two by the through bolts which hold the starter together.

Someone mentioned the issue of misalignment when reassembling the starter which is a possible here, given that you don't know the bike's history. I would tend to discount that possibility but it is not impossible that the PO had the starter through bolts loose and didn't realign the starter. It is not rocket science and just takes some looking and patience in shifting the end cap alignment before tightening.

Back to the brush holder plate: this is perhaps the most common problem with the small Japanese starters which use this system. I have repaired dozens of 4 cylinder GoldWing, ATV and so on starters of this type which had a bad connection because of corrosion where the three different metals are clamped together: cadmium, steel, aluminum. Moisture and time does the deed.

To correct it is necessary to partially disassemble the starter which is not a difficult operation for someone familiar with electric motors. The contact areas of the three components need to be cleaned and the unit realigned and assembled. I make an "L" bracket from a bit of steel to connect between the field housing and brush holder plate which requires some careful drilling and threading. Others make a cable gound strap. You can likely find a procedure on the net as I have posted this several times over the years.

Chores await, HIH

Norm

looks flat and round to me?


I don't think you would be able to kick start this GS with your hand, but maybe it's not properly tuned as you said

The bike has been sitting for a very long time. So I had it serviced just now, valve adjustment and also to resync and tune the carbs. Don't know if he cleaned them though.
Bike runs great I must say.

I went down to where it's stored to check out the battery but that's fine, 12.8V,
I also tried to start it a few times.
Sometimes it spins around slowly, but most time it spins around like it should.
Here's a "slow" start:
http://s2.photobucket.com/albums/y41/nexxuz/GS750/?action=view&current=VIDEO0014.mp4

Then another try, fires up imediatly...
http://s2.photobucket.com/albums/y41/nexxuz/GS750/?action=view&current=VIDEO0016.mp4

So I don't know how concerned I should be, 'cause most of the times I tried to start her up it's fine.

 

[Spiff]

I know this is a really old thread but I guess I can let you know how it went. As described in my project thread the starter solenoid all of a sudden burned up, the connectors where corroded and where looking pretty bad. So that was probably the cause of it starting easy sometimes and harder to start other times. Since I replaced the starter solenoid it has been spinning good for a long time. Untill now, but thats another thread: http://www.thegsresources.com/_forum/showthread.php?p=1678412#post1678412

also I did a compression test with a result of 140psi across all cylinders, so I guess this bike isn't a high comp after all... oh well

 

[Guest]

Move the exhaust cam to give it more overlap. Cylinder pressure will go down.

 

[Spiff]

Move the exhaust cam to give it more overlap. Cylinder pressure will go down.

I'm curious, why would I want to do that?