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Sputtering 71' 650 Tiger #783810 09/09/19 12:07 am
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Juan Cisneros Offline OP
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So tell me if you've heard this story before.
Bike was running fine then all of sudden its not. smile

Starts up fine, plugs good. But after about more than a 1/4 turn on throttle it sputters. I have to keep the speed down in order to keep bike going. Only thing I changed on carb was new float bowl bots to the allen wrench ones.
Any help would greatly be appreciated


1971 Tiger 650
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Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #783813 09/09/19 12:24 am
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quinten Offline
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Has it happened more than once ?
Like every time it gets nice and warmed up ... under load ?
... then it could be a partial seizure ?

Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #783814 09/09/19 12:32 am
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Juan Cisneros Offline OP
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It’s happen twice. Yes, when it’s warmed up. Partial seizure?


1971 Tiger 650
Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #783829 09/09/19 3:06 am
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Starving for fuel......how is the breather hole in your fuel cap?
Also you need to check your floats aren't jammed down with the increased torque you can get out of allen bolts. You may have distorted bowls, use a plate of glass and check them. If they are distorted, don't sand them, instead make up a plate puller.

I think John Healy may have a thread on here how to do it?

But a plate of clean steel [1/4" or better thick] with a hole through it, bolt the carb face down to the plate through the drain hole with a big bolt, use feeler gauges under the high spots [allen bolt locations?], then tighten the big bolt up, but don't get too aggressive. Remove often and check on your plate glass...keep doing this till your bowls are flat.

Trick is to straighten your carb surface without distorting the drain hole thread., that why you don't get too aggressive, and go slow and methodical, working up to it, even experimenting with the feeler gauge thickness a bit.

Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #783901 09/10/19 11:00 am
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Look for loose wire connectors. You would not be the first person on this board to report this symptom and have it be as simple as loose connectors. Vibration at certain RPMS will cause the connectors to "dance" and loose their connectivity. Get a pair of pliers and snug up all the ignition wiring connectors.


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Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #783920 09/10/19 3:52 pm
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Hi Juan, Did you remove float bowl? Make sure the gasket is not fouling float & needle & pivot are all aligned correctly.

Also you will get this if the main jet falls out. Check that main jet is tight. Generally the fallen out main jet bike runs good until near half throttle though. Took me awhile to figure that one out back in '74.

This is also symptom of the needle clip winding it's way up the spring in throttle slide or the clip loose on needle & needle slid up clip.

Don


1973 Tiger 750
Re: Sputtering 71' 650 Tiger [Re: TR7RVMan] #783938 09/10/19 9:17 pm
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Juan Cisneros Offline OP
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Originally Posted by TR7RVMan
Hi Juan, Did you remove float bowl? Make sure the gasket is not fouling float & needle & pivot are all aligned correctly.

Also you will get this if the main jet falls out. Check that main jet is tight. Generally the fallen out main jet bike runs good until near half throttle though. Took me awhile to figure that one out back in '74.

This is also symptom of the needle clip winding it's way up the spring in throttle slide or the clip loose on needle & needle slid up clip.

Don

Hi Don,
Thanks for the response. Yes, I took out the carb, and made sure the aforementioned possible issues. Clip and needle were fine and spring sitting on top as usual. Would a clogged gas cap be an issue. I do notice when I go for a ride and come back or stop on the side of road and try to blow through small hole, it wont go through. What could cause a clogged gas cap? I put a wire through and then it blows through easy.


1971 Tiger 650
Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #784316 09/15/19 2:39 am
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Juan Cisneros Offline OP
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UPDATE**
Bought a new throttle cable which was extremely in bad shape. Was making the slide stick a little. Also moved the needle clip to the last groove and what do you know bike runs great. Thanks for all the responses. Until next time I have an issue smile. #NextWeekend


1971 Tiger 650
Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #784326 09/15/19 4:25 am
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Hi Jaun, Good to hear you are running good!

When you say last groove, what does that mean? The bottom groove on needle or top groove on needle?

Good you did throttle cable now as I expect it would have broken soon anyway causing great danger while ridding. Especially if it stuck open.

With California fuel the bikes generally run better with clip on bottom groove of needle. However.... A big however, the needle wears most at a certain spot where you often have throttle when riding. Most often about 3/16-1/8 throttle. This small amount of throttle is where most of our riding occurs. Even on freeway a surprising low opening. So moving clip can put you at a "new" needle position compared to throttle opening. This is why I'm curious as to which way you moved clip.

The needle usually drags slightly inside needle jet wearing it oval. Some times owner installs new needle & jet bike runs worse as it's now too lean for our fuel. Where the worn jet & needle passed more fuel making mixture richer. 10% ethanol 91 fuel we have tends to like 5% larger jets across the board.

I wonder if something besides cable & clip position was the root problem? This got inadvertently corrected during cable replacement??

In any case if it's running good, it's good. Proof is in the pudding as they say.

Again happy you have a good running bike again!
Don


1973 Tiger 750
Re: Sputtering 71' 650 Tiger [Re: TR7RVMan] #784483 09/16/19 4:57 pm
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Juan Cisneros Offline OP
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Originally Posted by TR7RVMan
Hi Jaun, Good to hear you are running good!

When you say last groove, what does that mean? The bottom groove on needle or top groove on needle?

Good you did throttle cable now as I expect it would have broken soon anyway causing great danger while ridding. Especially if it stuck open.

With California fuel the bikes generally run better with clip on bottom groove of needle. However.... A big however, the needle wears most at a certain spot where you often have throttle when riding. Most often about 3/16-1/8 throttle. This small amount of throttle is where most of our riding occurs. Even on freeway a surprising low opening. So moving clip can put you at a "new" needle position compared to throttle opening. This is why I'm curious as to which way you moved clip.

The needle usually drags slightly inside needle jet wearing it oval. Some times owner installs new needle & jet bike runs worse as it's now too lean for our fuel. Where the worn jet & needle passed more fuel making mixture richer. 10% ethanol 91 fuel we have tends to like 5% larger jets across the board.

I wonder if something besides cable & clip position was the root problem? This got inadvertently corrected during cable replacement??

In any case if it's running good, it's good. Proof is in the pudding as they say.

Again happy you have a good running bike again!
Don


Hey Don,
The bottom groove from the top. I have a 3 groove needle. It was originally on top groove when I took off carb.
So my cable was in bad bad shape, but I'm not sure that was the issue. I hope it was. But I also thought it was running lean so I put the needle clip at the bottom. It doesn't sputter anyone on 1/4 throttle in first gear and runs quite fine. Now I need to check plugs after a long ride. Technically will the plugs be black now since the needle clip is at bottom or a pale color? mixture screw is 1 1/2 turns out. Idle is great. I'm tempted to put needle clip back on top just to confirm rm it was the clip and not the cable.


1971 Tiger 650
Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #784599 09/17/19 5:26 pm
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TR7RVMan Offline
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Hi Jaun, I don't know what the problem was really caused by, but lowering would be interesting to know. I do stuff like that.

However be careful as you can hole or break a piston messing around with mixture.

Almost certainly you'll want clip on bottom groove with California fuel.

Your main jet may very well be better larger also.

Plug readings are odd with our fuel. When bike is running perfectly, they will look like a bit too rich. Also to check at 1/4 throttle you must kill motor after riding at least a few minutes at that opening, kill motor & pull over. Not easy to find safe spot to do that. If you ride, 1/4 throttle & pull over without killing motor at 1/4 the plug reading will be skewed & not show 1/4 throttle.

The better way in my experience is use performance of motor & let plug color be what it may. However that takes a little practice. If plugs are dry & very sooty you are probably too rich. Can take some experimenting to get it best it will be. Moving the needle as you think is a good way to learn, just be careful.

If too rich you'll also get a blub blub in exhaust on gentle deceleration at lower speeds like in neighborhood. 8 stroking under harder acceleration. That's a misfire that sounds like bla bla bla. Goes away when backing off throttle.

Best way to find main jet is go too large, then when 8 stroking hard accell especially up a moderate hill on freeway, like to Carmel, go 1 size jet smaller until 8 stroking just goes away. Again our fuel demands a richer mixture that the 70s fuel.

As I recall you have Boyer. That is good because full advance of timing is 3500rpm while normal was 2000. This substantially reduces ping in the 1500-3200 rpm range especially up hill on slower twisty roads.

With Boyer & good mixture your bike will start first kick & run like a watch.

I don't recall what air filter you are using, but I strongly recommend the factory type gauze filters. They are still available & washable. Lasts for years. The bikes just tend to run better with them.
Don


1973 Tiger 750
Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #784603 09/17/19 5:44 pm
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C.B.S Offline
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Juan, did you fix the problem or is this still on going?

Last time we emailed you stated that it did not do this before?

So, something has changed...

Are you experiencing an over rich condition or fuel starvation?

Do you have a choke? If so, what happens when you engage it?

So many questions, I know but here to help


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Re: Sputtering 71' 650 Tiger [Re: C.B.S] #784615 09/17/19 7:04 pm
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Juan Cisneros Offline OP
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Originally Posted by C.B.S
Juan, did you fix the problem or is this still on going?

Last time we emailed you stated that it did not do this before?

So, something has changed...

Are you experiencing an over rich condition or fuel starvation?

Do you have a choke? If so, what happens when you engage it?

So many questions, I know but here to help

Bike starts first kick most times. I notice it takes a few kicks when bike sits after a ride. Maybe 30 min. Sits I got it running, I haven't really gone for a ride more than 10 miles. Im interested how the plugs will look. If its sooty, will putting clip on needle clip in the middle be a safe bet?
I use a gauze filter, which I clean pretty often. Battery is strong.
Like I mentioned earlier, I think the issue started one day when I was a straightaway and went over 50mph. I figured I opened it up too much and maybe drowned my carb with fuel. It had never happen to me before because I rarely go over 45 mph on rides.

Like I said, its running now so I will enjoy it until the next issue. As much as I hate when theres an issue, I like asking questions and trying new things out Its making me understand the bike a lot more. Plus you guys and the threads are so helpful. Love this community of british bike owners.


1971 Tiger 650
Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #784651 09/18/19 3:59 am
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...man; in my opinion as a guy who use these bikes as commuters, is that you NEED to use the bike more; longer distance and at more speed; if not there is no way you can conclude what could be right or wrong.
For example I have been changing plugs; checking at different stages, the carburetors (in my T140E) changing jets, checking the gasoline consumption; changing the timing of the EI etc all that take weeks or months due to you need to feel the stuff on the road AND into the city traffic; then conclude what s going on.
And do not forget, old vehicles need constant use if not start the problems; always. Humidity; corrosion; wiring; battery; the EI or points; the coils do not like humidity or too much heat and non of these things like not to be used.
Yes; I understand that your bike is possibly a hobby.

Re: Sputtering 71' 650 Tiger [Re: Juan Cisneros] #784655 09/18/19 5:01 am
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Hi Juan, The harder starting hot is normal with California fuel. I know you have the proper fat o-ring insulator between carb & manifold. That is important, but still it doesn't cure this problem. (the phenolic insulator block won't help more, trust me).

The solution to the hot start like you experience is two things. First don't use any throttle at all during first 10 min until bike fires, then add throttle & blip throttle to keep it reving until carb cools & it will idle normal. About 2 min or more depending on temperature.

The next thing sounds wrong & crazy.... But it's the only way that actually works. Tickle carb like when cold. No choke. Bring to compression. Turn on key. Hold almost full throttle (about 90-95% full). Kick very hard. Be ready to back off throttle as motor will race quickly. Again blip throttle until it will idle reliably, about 2 min. Don't do primer kick when hot like you might when cold.

If still no good, kick with zero throttle.

There is a bit of a knack to this, but once you get it, bike will start 99.9% of the time hot on first kick. All the guys I ride with do this & it works for everybody.

On a side note, many riders find they can kick harder & turn motor faster if they clock kicker lever to near horizontal. Do this by first freeing clutch. Then bring to compression. Raise lever, pull clutch, push lever part way down to near horizontal. Hold it there. Release clutch still holding lever there. Don't raise lever, keep it there. Now kick hard. This really works well. Many of us do this. Takes some practice, but soon is second nature. Even small light riders like me can reliably start bike like this.

I would most strongly recommend you don't move needle clip until you evaluate mixture by road testing with the tuning guide in your pocket. Mark your grip in 1/8s like a ruler with long & short lines using masking tape on grip & chrome part of throttle so you can see at a glance exactly how much throttle you are using at the moment. This marking is most critical & important. You cannot guess on this. You must mark.

Study tuning guide. Print it all or at least the parts about tuning. It takes some time to digest all that's going on with carb. Generally takes several road tests. Your road tests are way too short to get any reliable tests on running or reading plugs. You need to go a minimum of 20 miles just to fully warm engine. More if cold day. It must be fully heat soaked to evaluate mixture in all the riding conditions.

Ride & read guide. Ride & read guide. Repeat as needed until you memorize most of it & get a feel for what parts of carb does what. Then if you want move the clip. Then you'll not be guessing, but actually understanding why & what you need to do.

Here's the guide done by John Healy. The link doesn't look right, but it is indeed the correct link to guide.


https://www.princeton.edu/ssp/65-cub-data/library/amalbritbike.pdf

Don


1973 Tiger 750

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