1978 Yamaha SR 500 hard to start

YD3 · Posted: Sun Mar 27, 2011 7:00 pm Post subject: 1978 Yamaha SR 500 hard to start

Hello all,

Any SR guru's out there? I have owned this bike 7-8 years now and put maybe 1,500 miles on it. It has always been hard to start when cold or warm. Hot starting is not a problem, it cranks right up. For those familar with these bikes, there is a certain drill one must follow sort of based on an old British single. A SR friend is helping me check it out, but so far we haven't found anything. Here are the details; 165 lbs compression, new cam, new valves, fully charged battery, fresh gas, good plug, cam timing checked and correct, valves checked and in spec, hot blue spark at the plug. I believe that I have a clean carb. It has a new choke plunger in it. I have had the carb off about 10 times to clean it, can't find anything wrong and I clean it with an ultrasonic cleaner, blow thru the passagways, use carb clean after that, etc..

Mostly due to frustration, the bike sat most of the riding season last year so I have decided to try it again. I rolled it off, which is no easy feat, it went about 10 yards, hit, and settled down to a smooth idle. It acted as though I had rode it yesterday. When cold, I have to kick it 20-30 times to get it going. By then, I.m too tired to ride!!!

I believe it has a 36mm Mikuni with a header on it. It runs great, pulls great, and idles great once you get it going, but boy what a job!! The only thing that we have found so far is we think 165 lbs compression seems a little high but not sure why. Any ideas are welcomed. Thanks

CaptCatFish · Posted: Mon Mar 28, 2011 2:49 am Post subject:

Hi!

I wouldn't characterize myself as a SR500 guru but I currently have a '77 TT500 set up for flattracking (see pic) and am quite familar with the starting drill so perhaps I may be of some help.

For cold starts, I have a couple of suggestions. First make sure the idle screw is set very low, so low that you may have to increase it when the engine warms up. If the idle is set too high, it becomes very hard to start when using the choke. Also do not open the throttle at all when going through the kick start drill.

Second and perhaps the most important suggestion is to become very aware of the piston's top dead center (TDC) relative to the position of the kickstarter. Without using the compression release, push the piston through until it becomes almost impossible to go any further and hold pressure on it until you feel it let off just a little. (You should be at TDC at this point). Now return the kickstarter return to the highest leverage position possible that still engages the kickstarter mechanism.

For cold starts, I like to stand on a milk crate to maximize my body weight by having it as far above the machine as I can get it. Then (assuming I don't fall off the milk crate) I kick it all the way through in one fluid motion. Repeat the drill as necessary and it should fire within 4-5 times if everything else is a-ok.

I hope this helps. Please advise as to your success (or failure). If you reach a point of complete despair, there is no shortage of people who would love to buy that bike (I would be among them).

Good luck!

CaptCatFish

Russell · Posted: Mon Mar 28, 2011 3:10 am Post subject:

Not being clever enough to feel tdc on compression stroke through my foot I always resort to the method of putting the bike in second gear and pulling it backwards against the engine until it goes 'stiff'. Slip it into neutral and kick.

CaptCatFish · Posted: Mon Mar 28, 2011 9:59 am Post subject:

Never tried that Russell but I certainly will!! Great tip. Sounds lots more intelligent than my milk crate trick.

CaptCatFish

wfrpalm · Posted: Mon Mar 28, 2011 11:33 am Post subject:

I had a 77 TT500 with high compression and a cam and when I first got I couldn't get it to kick start either but once I learned the tricks It would kick start in one or two tries. Do just what the others say (TDC, smooth fluid kick). Don't try to kill the lever when you kick it. Good luck

passinglane · Posted: Wed Mar 30, 2011 4:28 pm Post subject:

With my '77 XT it is very important that you do not open the throttle even a crack. If you do that you will kick all day with no results. Leave the throttle alone, use the choke when cold and it should start with no more than a couple of kicks.

Bruce

SPRHK · Posted: Thu Mar 31, 2011 5:40 am Post subject:

In the distant past, I owned 2 SR 500's and a XT500 fitted with the 32MM SR carb. I currently own a SRX600. I always had excellent luck startinging them. It is all in the technique. Here is how I do it, and it always fires up on the first/second kick.
Make sure you are in neutral
slowly kick it though 2- 3 times
Turn the key on
bring it just past TDC and kick it!
Dont know why, but it always worked for me.

I had a customer who had an XL600R that would stall it and push it home because he could never restart it. Once he learned the technique, he was good to go. ALso, I am not 100% positive if it was the SR or the XT, but one had a warm start button on the carb.

gsbeliever · Posted: Thu Mar 31, 2011 11:56 am Post subject: drain float bowl?

I've learned that if any of my thumpers sat for more than a couple weeks, it paid to drain the float bowl(s) and refill w/ fresher gas from the tank. I've never figured out why gas goes bad more quickly in the float bowl than the tank, but it's always worked for me. Oh yeah, don't touch that throttle when kicking. Some guys inadvertently twist the throttle as they're kicking, causing much misery!
scott

YD3 · Posted: Thu Mar 31, 2011 7:23 pm Post subject:

Thanks everyone for the help. I know the starting drill is probably the most important part in getting this thing running. I believe that I was doing it correctly. But, to make sure, I have had another friend with an SR look at it as well. He can't get it to start from cold either. He has checked other parts of the bike to make sure they are correct. Valves, carb settings, timing, cam timing, choke function, fuel flow, battery charge, even resistance in the plug cap.

Now, let me explain further, this bike will start from cold after about 15-20 kicks. No throttle or choke needed. Float level, needle setting and size, jet size are all within spec. The other thing is, when the bike is warm, it will start 1-3 kicks. This is with me kicking. I'm 6'2" and 225lbs and I think I'm kicking hard enough.

I was hoping another set of eyes would help figure out the problem. Not so far, but we are both still plugging away. ( We have tried new plugs too!!) Please keep the ideas coming, we will try each one until we find it. Our next test is some sort of mixture analyzer that he has. I will post the results.

Thanks again!!

jayel · Posted: Thu Mar 31, 2011 8:22 pm Post subject:

a tight intake valve will cause hard starting check your valve clearances

YD3 · Posted: Sat Apr 02, 2011 2:10 pm Post subject:

The valves have been checked and they are in spec. My friend hooked a "color-tune" to the bike once it was running to check the mixture. It seemed to be pretty close. When warm 1-2 kicks and its running. I have checked and he has re-checked everything the manual says and everything we can think of. We do not believe that it is in the fuel system or any of the adjustments mechanically.

Now we are wondering about the coil.I have no idea how old it is, it could be original to the bike. With 165lbs compression could that be the item that won't let me start it cold? If you roll it @ 20 feet, it will fire right up cold. It seems as though we can't get the engine to spin fast enough or maybe long enough. I have had 4 different SR owners try to start this thing and they are all shaking their heads.

I hope someone has another idea, this one will cost me @ $180 to try.

Thanks

SPRHK · Posted: Sat Apr 02, 2011 3:03 pm Post subject:

If it was the coil, it wouldnt run at all. I have never had a coil do what you are experiencing. I would check to see if your choke is in proper working order. You might not be getting enough fuel during start up.

Russell · Posted: Sat Apr 02, 2011 4:29 pm Post subject:

I tend to think your problem is a combination of weak ignition and kick start technique when relying on cold kick star so that when your bike is cold and 'stiff', one swing through on the kickstart is not generating sufficient spark to fire up.I had an early DR350S that suffered from the same issue and from memory an auto electrician boosted the spark at kick-start by re-wiring a coil or coils down in the stator.LIke your SR my DR would fire right up if bump started and once it was warm. Sorry I don't have more specific information.

However I also have to relate that I have an over-bored XR250 Honda that I have great difficulty kick starting hot or cold. Last weekend a friend rode it for a day. He has a right foot educated by years of kick starting first of all BSA 500 singles, then XT500 Yamaha, and later XR500 and XR600 Honda's, now an XR650R Honda. The damn thing fired right up for him first time every time!

YD3 · Posted: Sat Apr 02, 2011 7:50 pm Post subject:

Thanks for the replies everyone. The carb has a new choke plunger in it. I would agree that it could be my technique that would not make it start, but I had 3 other guys who currently on SR's try it and they could not make it go either. Their bikes are all 2-3 kicks cold.

I have a 140 mile vintage ride tomorrow that I hope I can make. I think if I can get it to go in the morning it will do fine. Maybe it just needs a good shake down run!!

CaptCatFish · Posted: Thu Apr 21, 2011 11:34 pm Post subject:

YD3 - After feeling a little smug about how good my TT500 was starting and offering my advice in an earlier post, the damn thing has decided it has a mind of its own and won't start with less than 25 kicks and lots of swearing even with threats of a gallon of kerosene and a match!

I have another insight for you. Like your bike, my bike has the 36mm Mikuni on it. I'll bet you a nickel that your carb (like mine) is a Mikuni that was set up for a 2-stroke machine. If so, the needle jet (not the jet needle) protrudes into the carb body opening in the form of a "tower" surrounding the jet needle except for a place on the engine side. If the carb is set up for a 4-stroke engine, it will have an "emulsion tube" style needle jet that is flush in the carb body opening with tiny holes in it to suck fuel into the ventura. The difference being the emulsion tube needle jet "atomizes" the fuel differently for four stroke engines vs the primary style needle jet for two stroke engines which need more fuel. If your carb's needle jet is for a 2-stroke engine, it will make for hard starts and rich running all the way from idle through mid-range.

Apparently the lasting solution is to find the correct "emulsion" style needle jet and convert the carb. It has been done countless times although I have not done it myself but am investigating the options.

Jim