September 2011 6

Sir:may i ask you a question about motorcycle.My problem is that, 4stroke engine 125cc Honda,when i ride on the high way is OK,but when going down to the hill,it made sound like a gun fire,i have change new plug, and adjust the air screw . but it still make the sound like gun shot.Please help me to cope whit this problem.

If my English is not polite to you,pardon me for my mistake.
i am from myanmar(burma)
Matt

The bike is backfiring. If you are backfiring constantly while slowing down, then your jetting is slightly off. You need to run either 1 size smaller or 1 size larger jets. Being lean and being rich will both cause backfiring.

I have a small one cylinder Yamaha. It was given to my family and we have no information about it at all. I am searching for a manual for it, but the serial number on the stem below the handle bars is only 8 numbers long. Here it is: G5-204403

I understand that most Yamaha’s have 17 or so digits in the serial number. But I am certain this is the complete serial number, I have checked very carefully and there are no worn numbers. Any suggestions about where to find out what kind of bike this is so I can get a manual?

Notes from a Reader:
TRY SENDING SERIAL TO YAMAHA USA. I sent my serial number to Yamaha Austrailia (I am in Thailand and got the typical no response here) and they next day  told me cc engine and year everything as I was looking for parts for my 1984 Yamaha Belle Y80M.  I had located several other partial bike to peice parts from if they matched close enough.

Do you know if it is a 50cc, 80cc or 100cc engine?  any body markings, decals?  Is it a standard bike or is it a moped style with tank under seat?  I have several manuals 50cc 80cc and 100cc in Multiple languages but English is included

I’m working on a 1982 nighthawk 450. I have the tank off and drained but there is still a little remaining gas and rusty debris in the tank. How do I get this last little bit of fuel and rust out? (it wont dump out of the cap or the valve) Any info would be appreciated. Thanks.

The method I use is kind of brute force, but works pretty well. I remove the petcock from the tank then I put a few handfuls of spare nuts, bolts, and washers into the tank and shake it around to remove all the rust from the inside. As long as everything fits into the petcock whole, you’ll be able to get it all back out. Works great!

Electrolysis is another technique that works phenomenally well. My buddy just cleaned out a couple tanks, I’ll see if I can get some photos of the process from him. It’s a bit time consuming, but completely destroys all rust inside the tank. Works like magic.

Notes from a Reader:

I would suggest removing the tank from the bike then remove the fuel peacock. Once the peacock is out you can slosh the tank around and get the rest out. I would then get some kind of liquid cleaner (I use Simple Green Degreaser) and mix it up in a pail (or utillity sink) and fill, shake, empty, repeat until you have all the crap out of the tank.

Here in Canada we have a product called “Evaporust” avaliable at Canadian Tire that is in a liquid form. I put it in the tank (fuel peacock reinstalled and turned to “off”) and let it sit for at least 12 hours, then I flip the tank over and let it sit 12 more. I then remove peacock again and drain it all out and tape a shopvac to the holes for the fuel peacock and turn it on(with gas cap removed). I let the vacum pull air through the tank for 15 to 20 minutes and check to see if all the moisture has been pulled out of the tank.

Home Depot sells a simular product by Zep that can be diluted with water or put straight in as well if you cannot find Evaporust.

Be sure to clean the screen on the fuel peacock as well while you have it out.

I think my problem all along has been the ac generator. Everyone I’ve talked to has said this could be y I’m not getting any spark from my coils. Does this sound correct? Also i have the bike hooked up to the battery and everything is off and i came back to the bike and the ac generator cover was hot to the touch. Does this mean the ac generator is bad?

Notes from a Reader:

you should have a selenium Rectifier and CDI Ignition?  Power should go from battery to rectifier then to CDI and coils and generator from CDI 4 wires
Black ground
white to rectifier oposite of battery connection (Rectifier 2 posts current flows one way if diode is not shorted or open)
Orange coil Power
Black/red power

Positive lead on battery should have 2 leads one to rectifier and the other to switch

Does this help any?
you can try disconnecting yellow/red from generator as this is ac lighting supply and see if everything cools down.  if it does then there is short in lighting draining power.  with unhooked see if power to coil… could be issue!  tells you problem is in lighting. taillight, brakelight, headlight, all can be seperately disconnected to see where problem is.

Also from key switch Battery Voltage (red Wire) becomes brown.  Brown (I call Tan) feed power to everything on bike

I just rebuilt the carburetors on my GL1100 and reinstalled them on the bike. The bike in running but it won’t idle lower than 2500rpm’s.
Should I try synchronizing  the carburetors first and then adjust the fuel/air mixture pilot screws to fine tune?
The Clymer manual says I need to buy a portable tachometer when adjusting the pilot screws. Is this absolutely necessary?
Thanks for your help
Jeff

Hey Jeff

If your bike won’t drop down below 2500rpms then you most likely have a sync issue. Before you start messing with the sync do the following:

1 – Make sure your choke isn’t sticking or otherwise on. (Obvious, but a common issue)

2 – Make sure all your mixture screws are set the same. It doesn’t matter if they are set spot on, just make sure they are all set the same. Around 1.5 turns out from seated is probably a good ballpark for your bike, but you have the clymer, so set them to whatever it recommends for the stock setting.

3 – Make sure your throttle cable adjustment isn’t too tight. Verify by adjusting it loose and making sure the throttle mechanism on the carbs is hitting the idle adjustment bolt.

4 – Make sure your idle is turned all the way out.

If the above is all good and the bike is still running fast then it is time to sync the carbs.

I have a carb synchronizing article in the works. Once I get it online I can direct you to it. But you will need a proper tool/instrument to do a good job.

You do not need a portable tach to set the pilot screws. Just a keen sense of hearing to note when a change is affecting your idle speed.

Thanks for the quick response Evan.
1. The choke is working good.
2. I set the mixture screws to the clymer manual suggested settings to 1 1/4 turns out.
3. The throttle cable is working good and nothing is holding it up.
4. I turned the idle all the way out. The bike is running around 2000rpms now.

Does the float bowl adjustments have anything to do with the idle?

I have a 4 gauge sync kit and I’m going to sync the carbs today.

I will let you know the results.

Thanks for you help.

If your floats aren’t sealing well and the bowls are overfilling that could cause the same problem – you’ll get some extra gas into the cylinder.

If you’ve got the sync gauges I would just do a sync and see where it stands. Even a very slight differences in throttle plate adjustment (synchronization) can cause racing idle or hunting idle.

Please let me know how it goes.

I synced the carbs and the idle came down like you said it would. I adjusted the idle to 1000rpms and it idles very smooth.

When I rode the bike to work yesterday I noticed a hesitation in the middle throttle range. It seems to get worse as the bike warms up. I’m going to run a fresh tank of gas and add some Seafoam to see if this helps. Please let me know if you have any suggestions for this issue.

I rode the bike about 100 miles over the past few days and the hesitation is really bad at 1/4 throttle. Like I said in my last post-It get worse as the bike warms up. The bike pulls hard when I open the throttle but when I ride at a consistent speed at that 1/4 throttle mark it really runs bad.
Could the floats be causing this problem?

Are you running a stock exhaust? What is the condition of your air filter? Has the bike always been in your area/elevation?

If your exhaust has a leak (or your intake) it can cause odd problems like this. Verify the integrity of the exhaust and make sure it isn’t leaking or rusted through anywhere.

Hesitation as you describe can be caused by a variety of things. Around 1/4 throttle is where fuel metering is switching from the pilot circuit to the main circuit. A common cause is incorrect jetting. You may need to up the size of the main jets. What size jets do you have in there now?

How many miles are on your bike – are the main needles worn? They become hour-glassed over time rather than a straight taper.

Let me give you a little history of the bike.
I’ve owned the Wing for the past 7 years and I’ve put 35,000 miles on it. It currently has 63,000 miles.
I started having this problem last June and up until then I’ve never had a problem with the engine.
In August of 2009 I changed:
1. The timing belts
2. The air filter
3. The fuel filter
4. The fuel lines
5. The spark plugs
When I rebuilt the carbs I replaced all the jets that came with the Napco carb kit. Everything on the bike seems to be stock. I’ll double check the o-rings on the intake manifolds to make sure I don’t have a vacuum leak.

I am running the stock exhaust and it’s in very good condition.
I live in Michigan and I bought the bike from a guy in Ohio and he owned it for 8 years.
The only reason I rebuilt the carbs is because a mechanic at the Honda dealer told me it was a carburetor issue.

I really appreciate all your help.

Jeff

The problem is definitely carb related.

Are you sure the jets that were originally in the carbs were the same sizes as the ones provided in the rebuild kits?

You’re on the right track checking for vacuum leaks. You can spray WD40 all around the rubber manifolds and listen for any running change from the bike – if any gets sucked in it’ll rev higher.

I would also recommend double checking your float heights. They might be slightly high, keeping too much fuel in the bowl, causing a slight flooding condition.

Keep plugging away, it’ll be worth it!

I took the carbs off and put the old jets back in.
I lowered the floats so they would hang lower in the bowls and I re-synced the carbs.
The bike is still doing the same thing. A few people on the Goldwingdocs site think it might be a CV Slide issue. Is there a way to check the function of the slides when they’re on the bike?

I put 300 miles on the bike in the last week and the only time I have trouble is still at the 1/4 throttle range. It does the same thing when I accelerate and decelerate.

I checked the CV Slides and they move freely in the chamber. I did not mix the CV Slides up when I rebuilt the carbs.

I didn’t change the Air Cut-Off Valves when I rebuilt the carbs. I checked on the Randakk’s site and they said this could be part of the problem along with the CV Slides.

When I get the bike over 6000rpm it starts to hesitate the same way as the 1/4 throttle issue.

Sounds like you’ve got a bit of a pickle in your hands.

It also sounds like you’re close to solving it. The air cut off valves seem like a likely culprit. The symptoms match up as well – the cut off valves control air flow in the pilot circuit, so up to about 1/4 throttle. They also should activate in a high vacuum or air velocity condition, such as full throttle. If they aren’t working properly I can see this causing your problem.

If the problem persists past the air valve and I was in your shoes I would probably start watching eBay for a spare set of carbs for the bike. Rather than replacing each of the carb parts individually it’ll be much more cost effective to replace the entire set with another good condition rack. If it proves not to be the problem then you can resell them or keep them long term as spares.

Someone once told me “carbs are more of a magic than a science” – and it has always stuck with me. Sometimes it seems like voodoo art getting all the kinks worked out!

Keep working at it and keep me posted!

Firstly, Hey guys!

Secondly..I just got my permit and a friend of mine was giving me a basic lesson on riding. He has an 81 Kawa LTD 440. Things were going pretty well until I laid the bike on its side at around 5-7 mph.

Bike still runs but as of now the carbs are spitting fuel out of one of the hoses running off the back. I feel really ****** bad and im trying to research probable causes and fixes in hopes its nothing major.

If anyone has any ideas I can throw his way it would be GREATLY appreciated. I want to be able to at least help him fix the problem since i cause it.

Thanks in advance,
Doug

Notes from a Reader:
here is a quick fix that sometimes works without having to do any disassembling,what has worked for me in the past for a fix when that happens is at the bottom of the carburetor bowl on the side there is a Philips head screw when you loosen that it will let the gas dump out(drain)the carburetors bowl of fuel it will sometimes remove the dirt or debris that is causing your float needle valve from closings just loosen that screw until the gas is flowing out the overflow tube(the one you say is leaking anyways) and while it is leaking the gas out shut off the petcock on the gas tank and let the gas drain out of the tube until no more comes out then tighten the screw and turn the gas petcock back on while either tapping on the carb or shaking the bike side to side,that usually frees the piece of crap that is causing the float needle from closing,or worse comes to worse you will have to take the carbs off and remove the bowl that is leaking and clean out that carb,try it i think it will work the easy fix

Notes from a Reader:
It is possible that there’s a leak in your gas tank. So, I suggest that before using the bike again, have a car repair expert check it. Gas leak is pretty dangerous that’s why auto manufacturers announce recall whenever there’s a mechanical defect in the car that causes it. A good example of those car manufacturers is Ford. The Motor Company said last Monday that it is set to recall 1.1 million truck pickups. The recall will contain the F150, which is the automaker’s most popular model in the U.S. The recall concerns rust of the fuel tank straps. There’s a chance of fire should the tank drop from the vehicle. Here is the proof: Ford recalls 1.1 million pickups for fuel tank issues.