Cold start problems

[gsryder]

I have read through here on the cold start issue and I am still having trouble.

I did the relay mod no difference.

1981 GS750, pods, 4 into 1 kerker, proper jetting, other than that basically mechanically stock.

In the morning or after sitting for a period of approx. 8hrs or longer the bike will not start. Choke or no choke it will sputter once then immediately die.

Two squirts of starter fluid on the pods and it will fire right up and then be good for the rest of the day.

As long as it is responsibly warm or has been ridin in the last 6 to 7 hours it will fire right up and run perfectly.

I am at a loss and I hate having to carry a can of starter fluid everywhere I go.

I was thinking about checking the valves but wouldn't it run crappy if they were out of adjustment?

Any help would be appreciated.

 

[Guest]

-Could be tank cap vent blocked, try loosening it before starting.
-Did you try petcock on prime?

 

[twr1776]

gsryder Cold start problems I was thinking about checking the valves but wouldn't it run crappy if they were out of adjustment?

I would check the valves first then go on to weak spark, etc. Bad starting is a classic sign of valves needing adjustment. When were they last done and did you do them yourself?

 

[focus frenzy]

OK, now for a useful reply.
I suspect you are actually on the lean side on the pilot jetting. the "choke" system on the CV carbs actually just adds some more fuel via a bypass port. the amount of fuel it adds is fixed and can't easily be changed without drilling the tube that sticks down into that side hole in the carb bowl. (very tiny drill bit)

if the the cable is adjusted correctly and is pulling the "choke" plungers to full stroke and the passages and jet tube is good and clean a switch up a size on the pilot jet is in order as low speed pilot jetting is where the cold start mixture is adjusted.

my 1000G was reluctant to start when the temps got below the 60's and if it got down to the 40's it wouldn't start at all. going up one size larger on the pilot jets cured it.

 

[gsryder]

I dont have a choke cable I just hold it open manually when starting.

That makes allot of sense on the pilot jet. I did not change that when I rejetted.

How much bigger would you suggest going on the pilot?

 

[LarryA_Texas]

me, too

me, too

I have a GS650 with the exact same symptoms. I have changed the pilot jets up one from 140 stock to 142.5. It may be helping a little but still just turns and turns with barely a puff.

The only way it starts is with no choke and a little throttle; just barely cracked open. One odd thing that seems to help is blowing into the vent tubes. Fires right up after that.

I did check the valves to spec...they're all good.

I have the next larger pilot jets (145) and am going to change them today to see if it helps. Took the plugs off and the tips are white...very lean white. So you'd think that it's so lean that bigger jets wouldn't be any problem at all. My only reluctance there is the choke.

If you pull the choke while it's cranking all the little 'puffs' of attempted ignition go away. If enriching with the choke doesn't help, in fact makes it worse, why would bigger pilot jets help? Even if that confuses me, it's worth a try.

 

[trippivot]

Cold start problems are an indication that your cam tensioner is out of adjustment. the cam timing is the most important when the engine is BONE COLD..\


I read all the posts in this thread I do not think I have seen a 140/142 pilot jet.

the enrichener circuit is a complete fuel circuit. if the pick up tube is usually not cleaned properly the plungers need to be removed and the passage needes to be as clear as possible. Drilling the brass tube has been suggested but I NO.

after that the ignition timing has to be at the F mark a new set of plugs is always a good idea - cleaning is not enough some times. the plug caps may have excessive resistance but that is 4 down the list. battery voltage while cranking the starter should be checked for load issues of a weak battery(lower than 10.8 volts will make trouble)

 

[focus frenzy]

HOLY MACARONI!!! 142.5 pilot jet!!!! the stock main jet is only a 110 (97.5 on the E model, hmmm interesting) and acording to suzuki the stock pilot jet is a 42.5.

if pulling the chock makes it worse the choke circuit is not getting any gas and besides gas the choke adds air.
there is a itty bitty jet like object in the bottom of the port in the carb bowl that does clog with the fine silt goo that gets past the tank screen and the float seat screen, and the choke pick up tube is also prone to clogging.

 

[gsryder]

I am running a 132 main with the needle shimmed up just a hair and the timing advanced ever so slightly.
Bike idles and runs strong once it is started doesnt even need to be warm once its started runs smooth no back fire or sputtering.
I am going to try the pilot jet first.
I called down to the local bike shop and they said they have the pilot jets in stock.
I will try to go up 1 size and see if that helps.
I am still going to check the valves also.
I just printed off the 16 valve adjustment info from basscliffs site.

 

[Larry D]

If you're going to adjust the valves. I highly recommend getting these feeler guages (or some like them). Much easier to use in the tight spaces than regular straight feeler guages.

http://www.motosport.com/dirtbike/p...ogId=108691&CAWELAID=291261379&segment=badger

 

[Guest]

not sure about the jetting, but cold start issues is a classic sign of tight valves.

 

[LarryA_Texas]

HOLY MACARONI!!! 142.5 pilot jet!!!! the stock main jet is only a 110 (97.5 on the E model, hmmm interesting) and acording to suzuki the stock pilot jet is a 42.5.

.

Sorry...drop the 1. I've seen some lists where the pilot is 40 and some where it's 42.5. I also have a set of 45 s that I have not put in yet.

 

[Steve]

I have just read through all the posts so far and noticed a rather distinctive trend.

I have read through here on the cold start issue and I am still having trouble. ... In the morning or after sitting for a period of approx. 8hrs or longer the bike will not start. ... Two squirts of starter fluid on the pods and it will fire right up and then be good for the rest of the day. ... As long as it is responsibly warm or has been ridin in the last 6 to 7 hours it will fire right up and run perfectly. ... I was thinking about checking the valves but wouldn't it run crappy if they were out of adjustment?

Just thinking about it isn't going to get it done. Run crappy? Not necessarily, once it gets going. The aluminum in the block and head expand as they warm up, getting the valves to their intended clearances. The problem only exists when cold because the valve clearance is tight, causing late closing of the intake valve, allowing some of the mixture that has been drawn into the cylinder to be pumped back out, into the carb throat. That mix goes back past the jets, picking up more fuel, because the jets only see moving air, they don't care which way it's moving. The next intake cycle, that air in the carb throat that has had extra gas added now goes back past the jets a third time getting even more gas. Now you have a super-rich mixture and the compression in the cylinder is down because of the valve timing problem, and it just does not want to fire. When the engine is warm there is more clearance on the valves and timing is such that the timing is not affected as much and compression is not reduced, meaning that you can start the bike when it's warm.

]I would check the valves first[/color] then go on to weak spark, etc. Bad starting is a classic sign of valves needing adjustment. When were they last done and did you do them yourself?

OK, now for a useful reply.
I suspect you are actually on the lean side on the pilot jetting. the "choke" system on the CV carbs actually just adds some more fuel via a bypass port. the amount of fuel it adds is fixed and can't easily be changed without drilling the tube that sticks down into that side hole in the carb bowl. (very tiny drill bit)

Useful, yes, but not sure it applies to the problem at hand.

The only way it starts is with no choke and a little throttle; just barely cracked open. One odd thing that seems to help is blowing into the vent tubes. Fires right up after that. I did check the valves to spec...they're all good. ...

Not sure about your problem, Larry, but I can't see myself living with puffing into the vent tubes every time to start the bike. I know the priciple behind it, I have actually done it on a bike and, yes, it works, but that is a band-aid for a problem that should not exist.

Cold start problems are an indication that your cam tensioner is out of adjustment. the cam timing is the most important when the engine is BONE COLD..\

As much as I respect your expertise, I'm not sure I can agree with this. In my experience (considerably more limited than yours, I'm sure), I have not seen a tensioner out of adjustment, causing a cold start problems.

... I am still going to check the valves also.
I just printed off the 16 valve adjustment info from basscliffs site.

not sure about the jetting, but cold start issues is a classic sign of tight valves.

There are a couple of other opinions (to which you are certainly entitled), but the overwhelming response is CHECK YOUR VALVE ADJUSTMENT.

I have had various bikes over the years and found that they ALL had problems starting cold ... until I adjusted the valves. Once the valves were adjusted properly, it seemed that I did not even had to push the starter button, I only had to think about pushing it and the bike started. Yeah, it's that much of a difference.

I am not sure that changing pilot jets will help in this situation. From what I have seen on this board, the pilots are rarely changed. Even with the popular DynoJet kits, they leave the stock pilot jets. Yes, there are times that going up one size can help, but I don't think this is one of those times.

Add this opinion to those previously expressed, but there is a bit of experience behind it, too.

.

 

[Larry D]

Steve, I concur, 100%.
When you have a bike that you don't know the history of, or you just purchased it, there are two things to do first.
Clean the carbs as per direction on this site and adjust the valves. This tends to solve alot of issues. While your doing these two required tasks, you'll learn more about the mechanics of the particular bike. You may find the po left a ham sandwich in there.......

Cleaning the carbs and adjusting the valves establish a baseline to work from.

 

[LarryA_Texas]

pilot jets

pilot jets

I tried the next size up on the pilot jets and it got worse: didn't start at all. Pretty much as expected. That was with 47.5 which was two sizes up. I've gone back to the 45s and will check again as soon as I have some time to make sure I didn't screw up the valve adjustment. It's certainly possible.

Two things that make this confusing; the stock pilot jets for the 650 on some lists are 40, on others they are 42.5. I've heard that they were very lean so it makes sense to go up a step. Besides, my plugs were dry and very white. Like paper white. so I believe it is running very lean and going up a step on the pilots won't hurt anything there.

Second: While attempting to start you get some ignition when you first push the starter; only for a second; and then only an occasional stutter. But even though it's very lean, pulling the choke out during start attempts completely stops those occasional little puffs of ignition. It also stops sputtering when you close the choke and open the throttle. The only way to get it to start is with no choke and 1/8 of a twist on the throttle and hope those little puffs of ignition become frequent enough to actually start it before the battery dies.

One other thing today; I wired from the battery directly to the coils to make sure it wasn't a voltage drop problem through the system. It made no difference.

I know everything points to a valve problem and I'm going to get back into them to make sure. But I have adjusted them to specs. Maybe I missed something there. Maybe it's time to consider the other possibility; that the shims are correct but the valves are leaking anyway. I recall the compression test was good, but don't remember the numbers right off. Next chance I get...

 

[Steve]

LarryA, you have come in on gsryder's thread with a similar problem and we are getting confuzzled on what advice we are giving to whom.

You have tried some different jets, but please tell us a little more about your bike.
Is it stock, or does it have pods and/or a pipe?
What main jets are in it?
How many turns out are the idle mixture screws? :-k

The answers to these questions will help determine what jets you might need.

.

 

[LarryA_Texas]

LarryA, you have come in on gsryder's thread with a similar problem and we are getting confuzzled on what advice we are giving to whom.

.

Good point. Since it's the same problem and he asked how far up to go with his jets, I had in mind that I was answering his question by telling him that 47.5s didn't help me.

I wasn't really asking for advice. I know I have to recheck the valves and see if maybe I missed something there.

Sorry to confuzzle.

 

[gsryder]

I appreciate all the responses and yes I am going to check the valve clearances hopefully this weekend. I suspect they are in need of adjusting. I just got my new tires in today also so I have plenty to do. I will keep you guys posted on the results.

Thanks again for your help.