A Cure for Hard Starting 16 Valve 750 Engines

[almarconi]

I don't start many threads in the forum but I thought I would pass on this bit of knowledge.

For the last couple of riding seasons, my bike has been hard to start. I did the usual carb cleaning,valve adjustment, coil mod, upgraded coils..etc. In order to get it running, I usually had to blow into the breather tube. Once the bike was warm, it would restart no problems. The more I drove the bike, the more difficult it was to get started.

Determined to finally "fix" the problem. After riding for 6k miles, I decided to check my valve clearances again. The clearances on valves 2 and 3 were within spec but the clearances on 1 and 4 were too tight. The cam lobes looked slightly discolored. I readjusted them to the loose side of clearance. Went to start the bike and guess what, it started right up. I figured I got lucky so I let the bike sit for a few days. Went to start bike and it started right up.

Lesson learned CHECK & ADJUST THOSE VALVE CLEARANCES

Can't stress enough what a difference this has made. I tore those carbs down 3 times convinced it was a carb problem causing the hard starting. I'm thinking that it would be prudent to check the valve clearance on this bike every 3k miles, 6k miles is too long an interval. I'll probably just do it every time I change the oil.

 

[Nessism]

Glad to learn you fixed the bike. Do you know what when wrong when you adjusted the valves the first time, or did you just wait too long between adjustments?

Honestly, for the life of me I can't understand how some people feel valve adjustments are optional maintenance. Hard starting is the least of the engines problems if the valves are not adjusted regularly - the valves will burn. Many GS deaths can be directly attributed to user neglect in this area. Damn shame.

 

[spyug]

Very good reminder sir. Much appreciated.

I think the problem for many is that it appears to be that kind of project that is difficult and too time consuming. Of course its not.

I haven't done mine on the 750 but did do the ones in the Kat engine. I'm finding the 750 a tad harder to start even with the coil mod so I was thinking its time for a valve adjustment.

With the Kat project stalled and riding season on us I guess I better buckle down and do those valves now.

Again thanks for the reminder.

cheers,
spyug.

 

[Nessism]

I haven't done mine on the 750 but did do the ones in the Kat engine.

How long have you owned that 750? Isn?t that your main ride?

 

[Steve]

I fully agree, but must also say that your post title is not quite complete. :-k

It's not only the 16-valve engines that benefit from valve adjustment.

8-valve engines are also hard to start when the valves are tight.

The 16-valve engine are easy enough to adjust the valves, just remove the cover and adjust the valves. The 8-valve engines will likely require some shim replacement, which will intimidate some. Yes, there is a lovely chart in the service manuals to tell you exactly what you need, but even I find that chart frustrating. That was the origin of my spreadsheet.

I sent out my 338th copy this morning, still have plenty left. Feel free to follow the instructions in my sig to get yours.
(Note that the spreadsheet will not benefit riders whose bikes have screw-type adjusters on the valves, but if you ever work on another bike that uses shims, it might be handy to have on hand.)


.

 

[TheCafeKid]

I fully agree, but must also say that your post title is not quite complete. :-k

It's not only the 16-valve engines that benefit from valve adjustment.

8-valve engines are also hard to start when the valves are tight.

The 16-valve engine are easy enough to adjust the valves, just remove the cover and adjust the valves. The 8-valve engines will likely require some shim replacement, which will intimidate some. Yes, there is a lovely chart in the service manuals to tell you exactly what you need, but even I find that chart frustrating. That was the origin of my spreadsheet.

I sent out my 338th copy this morning, still have plenty left. Feel free to follow the instructions in my sig to get yours.
(Note that the spreadsheet will not benefit riders whose bikes have screw-type adjusters on the valves, but if you ever work on another bike that uses shims, it might be handy to have on hand.)


.

Ohh I see you havent done many of these Frankly, its just as time consuming as the 8V motors...

 

[spyug]

Ed, you are , as always, correct. I'm sad to say that I've had it going on 4 years now and haven't touched the engine. Mind you the PO had done them about 2000 km previous to me getting her ( then it sat for 7 years) according to the records and I've only manged about another 4500 Km since putting her on the road.

I must admit I was one of those who shied away from the project, that is until I did the ones on the Kat engine. They are calling for a long rainy weekend so I might just find the time to do them.....that's if I can get out of house 'chores" and don't get bogged back down in the Kat project which I desperately need to finish.

Its definitely on my bike "to do " list.

cheers,
spyug

 

[tejasmud]

One thought on doing valve adjustments is when a bike has sat for several years. A non runner upon purchase, and especially one out in the elements uncovered.

Say the bike is gone through, carb clean/dip, o-rings, ect, ect, and valve adjustments are completed before firing the machine up and putting it on the road that it might be a good idea to plan an early valve adjustment or at least check them after it has run a hundred miles or so.

Thought behind this is while the engine sat some of the valves remain in the open position. The exhaust valves may be more subject that tend to get carbon crusties and/or rust build up on the valves. Valves being in this state and adjusted before the engine is run enough to clean them off might skew the adjustment after debris has been blown out.

The #5 exhaust valve had been gunked up pretty bad on the 700, and didn't want to close. I noticed it needed about 1 to 0.5mm more adjustment than the others when adjusting initially. I was thinking bent valve initially, but it wasn't. Had I not pulled the top end and just continued the course of adjustment then buttoning it up believing all is well there would have been issues. Toasted #5 exhaust valve for sure.

I would say it is probably better to run it after a bike has sat, then do adjustments.

Anyways just a thought.


E

 

[Mercaholic]

Glad to learn you fixed the bike. Do you know what when wrong when you adjusted the valves the first time, or did you just wait too long between adjustments?

Honestly, for the life of me I can't understand how some people feel valve adjustments are optional maintenance. Hard starting is the least of the engines problems if the valves are not adjusted regularly - the valves will burn. Many GS deaths can be directly attributed to user neglect in this area. Damn shame.

I am ashamed to state that I need to look at all of my GS's too but with now 5 in total, I'd need to set a long day aside. Just the thought of getting organized fatigues me....lol

 

[Steve]

Ohh I see you havent done many of these Frankly, its just as time consuming as the 8V motors...

True, the process of actually adjusting the valves isn't any quicker (besides, you have twice as many to do), it's just that when you are done, you are DONE. You don't have to wait for your new shims to come in the mail, then go back in and change them.

.

 

[bwringer]

If you have a decent shim collection handy, adjusting eight shim valves goes MUCH MUCH faster than fiddling with 16 screw type adjusters.

Once you have a handle on what shim sizes are in your engine and what you might need in the near future, it doesn't take long to accumulate enough to cover most situations.

Whatever type you have, I agre -- valve clearance checks are NEVER optional. And hard starting is just the first symptom.

 

[Nessism]

If you have a decent shim collection handy, adjusting eight shim valves goes MUCH MUCH faster than fiddling with 16 screw type adjusters.

Once you have a handle on what shim sizes are in your engine and what you might need in the near future, it doesn't take long to accumulate enough to cover most situations.

Whatever type you have, I agre -- valve clearance checks are NEVER optional. And hard starting is just the first symptom.

I agree with Brian. I?ll take shims any day over threaded adjusters. It takes longer to get the valve cover off than to check and adjust the valves using shims.

 

[Guest]

Same goes for the threaded adjusters though...usually it's only checks, and occasionally a valve or two drifting toward the lower limit will need tweaked. Dealing with the gasket (Real Gasket) takes a lot of time due to the amount of degreasing/prep required to make sure it goes on dry etc., and makes the whole thing more of a hassle than it needs to be.

 

[salty_monk]

I'm with Brian too... I'd rather do an 8v engine compared to a 16v any day...

Dan

 

[crapwacker]

Am I correct in thinking that the adjustment interval is 1,000 miles (8 Valve) ?

 

[Nessism]

Am I correct in thinking that the adjustment interval is 1,000 miles (8 Valve) ?

It's about 4000 miles but please check your service manual to verify.

 

[almarconi]

Do you know what when wrong when you adjusted the valves the first time, or did you just wait too long between adjustments?

I think I simply waited too long (6k miles) between adjustments. I'm going to try 3k mile intervals and see how that goes. If the bike becomes hard to start, the valves will be the first thing I check.