TX650 Hanging Idle

[Mannyroad]

Hi guys,
Well, I took the TX out for my first ride on it since buying it last year. Went really well for a few miles, then suddenly the revs refused to return to idle. Hung around 3-3500rpm. Turned motor off and started it up again and initially it idles at around 1500, slightly erratic, but then gradually starts increasing till it hits 3000-3500 again. I've searched the forum posts and it seems the general concensus is its either a sticking advance unit or an air leak at the manifold. Haven't yey checked the advance but yanking the carbs suggests they are well secured to the inlet manifolds, so how do you guys check for leaks? Someone said spray WD40 all over the manifold rubbers to see if engine revs change but this is a really messy way of checking, no? Tbh, I'm a bit pissed off as I was rather hoping this would be the one bike that wouldn't give me hassle every time I take it out.

 

[Jim]

Someone said spray WD40 all over the manifold rubbers to see if engine revs change but this is a really messy way of checking, no?

Yes... very messy. I use electrical contact cleaner. It evaporates in seconds leaving absolutely no residue.

 

[Mannyroad]

Sounds a good idea Jim. I guess brake & clutch cleaner is a good equivalent. I have plenty of that.

 

[Jim]

I guess brake & clutch cleaner is a good equivalent.

Yes, I use that too. Anything that's flammable and evaporates with no residue works. Brake cleaner, carb cleaner... contact cleaner...

Was one guy here a few yrs ago recommended dribbling motor oil on the carbs and boots. Um... yeah, sure buddy.

 

[Mannyroad]

Yeah, know what you mean. It was my mate who suggested WD40, but wasn't kean to try that. Will go the brake cleaner route.

 

[Wingedwheel]

I’ve been having this exact same issue with no resolution yet. Consensus is a carb issue which I’m going to throw a spare set on pretty quickly to verify, otherwise I’ve cleaned, greased, put new springs on the weights and even shortened a spring. It behaved normally with the weights wired but if the different carbs don’t make a difference it looks like I’ll be installing an electronic iggy. I can get it close with the idle turned way down but it has to go down below 1K which is too low.

 

[Mannyroad]

I’ve been having this exact same issue with no resolution yet. Consensus is a carb issue which I’m going to throw a spare set on pretty quickly to verify, otherwise I’ve cleaned, greased, put new springs on the weights and even shortened a spring. It behaved normally with the weights wired but if the different carbs don’t make a difference it looks like I’ll be installing an electronic iggy. I can get it close with the idle turned way down but it has to go down below 1K which is too low.

I have an electronic ignition that I bought for my current chop build but decided to go rephase so stuck the iggy on FB, but hasn't sold yet, so maybe its telling me something. I think I will put it on the TX, which will rule out the advance. See how it performs then. The guy who did the original resto did a nice job and it looks like he stuck new carb boots on, but can't be sure unless I pull the carbs, but I'm trying to avoid having to pull airboxes off.

 

[Wingedwheel]

I'm trying to avoid having to pull airboxes off.

I’ve done it so many times it’s routine.4 bolts, 4 clamps, boom. Done.

 

[Mannyroad]

I’ve done it so many times it’s routine.4 bolts, 4 clamps, boom. Done.

Cheers for that. Took a quick look and saw the bolts. Simple job. Will check the boots out. Going to ditch the points and advance unit and fit the electronic ignition, so that takes the advance unit out of the equation.

 

[Jim]

Cheers for that. Took a quick look and saw the bolts. Simple job. Will check the boots out. Going to ditch the points and advance unit and fit the electronic ignition, so that takes the advance unit out of the equation.

A quick and dirty way to rule the advance out or in, is to safety wire the advance weights retarded so they can't move. Warm the bike up and see if you still have the hanging idle. If it still hangs, it's not the advance.

 

[Mannyroad]

A quick and dirty way to rule the advance out or in, is to safety wire the advance weights retarded so they can't move. Warm the bike up and see if you still have the hanging idle. If it still hangs, it's not the advance.

Good point. I shall definitely give that a try. Thanks Jim, hadn't thought outside the box like that, probs due to the frustration. But cheers

 

[Wingedwheel]

It behaved normally with the weights wired

So does that mean it is the advance or that my carbs are triggering it?

 

[Jim]

So does that mean it is the advance or that my carbs are triggering it?

Well it's not a definitive test, but think of it this way, if carbs are causing the hanging idle, they'd cause it no matter the condition of the advance, no?
Wiring the advance closed won't fix a problem with the carb(s).

 

[Jim]

Should have added, with the advance wired retarded, it might not hang quiet as high, but it'll still hang higher than it should. In other words, if it was hanging at about 3000 revs and wiring the advance only produced 2000 revs, it's still hanging, right?

That make sense?

 

[grouchie77]

how do you guys check for leaks? Someone said spray WD40 all over the manifold rubbers to see if engine revs change but this is a really messy way of checking, no?

That sounds like something I would say... I wouldn't be surprised if I'd had said that on here somewhere.

I've also heard opening the valve on an unlit propane torch, or the valve on the oxygen tank on a oxyfuel setup... "old farmers' tricks" I'm sure.

I have in the past just used a squirt bottle filled with water to see if that would drop the revs. If it works great, if it doesn't, that's ok too. But at least it didn't leave an oily mess all over my bike.

 

[Mannyroad]

Should have added, with the advance wired retarded, it might not hang quiet as high, but it'll still hang higher than it should. In other words, if it was hanging at about 3000 revs and wiring the advance only produced 2000 revs, it's still hanging, right?

That make sense?

Yes, perfect sense. Will give it a go before pulling carbs and airboxes. As my dad always said "try the easiest fixes first".

 

[Mannyroad]

That sounds like something I would say... I wouldn't be surprised if I'd had said that on here somewhere.

I've also heard opening the valve on an unlit propane torch, or the valve on the oxygen tank on a oxyfuel setup... "old farmers' tricks" I'm sure.

I have in the past just used a squirt bottle filled with water to see if that would drop the revs. If it works great, if it doesn't, that's ok too. But at least it didn't leave an oily mess all over my bike.

No, it wasn't you I was quoting, it was a mate of mine.

 

[grouchie77]

When the bike is warmed up and idling, squirt some WD-40 at various suspected leak spots, if the idle changes, it'll help you narrow down the source.

Yep, that was me. I knew that asshole sounded familiar.

 

[grouchie77]

My Dad taught me to use water, his reasoning was that if there is a leak, the worst that could happen is the engine stalls.

He said that if I used ether or engine starting fluid and a vacuum leak sucked that in, it could make the engine race and might cause problems.

 

[Wingedwheel]

it's still hanging, right?

I will have to go back to my notes but if memory serves me correctly I was able to set the idle and rev the throttle with no hanging.