Motorcylce Guys

[xrated]

I need some mechanical help here fellas.

I'm taking over my father-in-laws old bike now that he joined the dark Harley side. The bike is in great shape, fresh rubber and all, but last summer it developed a bog off of idle.

It runs fine at idle and fine once you get out of the bog, but it is a nasty bog and needs to be fixed before my wife and father-in-law will let me start riding.

The bike is either a 86 or 87 Yamaha Fazer. Not sure on the year but I will check tonight.

 

[Killerk]

Not real familiar with the carb set-up on the Phazer, but most likely that is where your problem lies.
How long has the bike sat since it last ran well?

 

[bonz50]

the early phazer was a pretty damn cool bike, pretty good ballz too for the type of bike it was... this had the lay down 5 valve genesis head on it, those motors were notorious to have a bog just off idle (all the 700/750cc 5v motors were, the 1000's not so much)... I would do a thorough clean job on the carbs, yank the rack and go thru 'em like you would a sled, pilots/mains/etc... if that doesn't clear it up then it is something that is the nature of this motor design... imho, i'd go ahead and ride it anyway as long as the rest of the bike is up to snuff...

 

[Gimpster]

Time consuming is the biggest factor here. The carbs are dirty. They are of the variable venturi variety and are most likely gummed up. Look online for a parts diagram to make sure you disassemble and reassemble them correctly and parts are not unaccounted for. The fuel air mixture screws have a spring, washer and o-ring in the port where they are removed. Often overlooked or assembled with the washer and o-ring the wrong way around causes issues. When cleaning carbs and blowing the passages the o-ring and washer may dissappear without you knowing if you don't know what you are doing during disassembly.
Variable venturi diaphrams can be gummy etc from setting so long. At least these carbs don't have air cut diaphrams on the sides of the carb bodies so that makes it a little easier and less expensive to repair because that diaphram kit per carb runs around $100.

Also the carbs need to be syncronized after assembled. Myself, since I am in the business, I digitally syncronize the carbs after reassembly.
I have done the carbs on quite a few of them over the years and they have no flat spot under acceleration when I am done tuning them

http://www.thegimpster.com


----- Gimpster -----

 

[bonz50]

to go along with what gimp said, check the diaphrams for tears... i've seen that happen on several yammies i've owned in the past... CV carbs are easy to tune but the stock jetting from the factory is often poor at best... pull the brass plugs that cover the mixture screws and it'll help you get 'em dialed in... a cheap carb sync can be had for about 75 bucks... worth its weight in gold if you want your bike running smoothly...

 

[Weekday Warrior]

dude,

I'd just pull the whole works and send it to gimp and be done with it

 

[Gimpster]

Hopefully someone never put Stabil in the tank and left it set for a few years. That stuff is only good for like 90 days. Sea Foam is about the best to add to fuel for prolonged storage. I have had a few ATVs come in that had stabil in them and the carbs were filled with a crystal substance after the stabil broke down. Another one... A Harley low rider parked with stabil and a quarter tank of fuel. The stabil gelled into bb's then expanded the tank and became rock solid. Only thing I found that would break it down was sea foam. That took 3 months of soaking. Carb dip wouldn't touch it

Here is my VacumMate I sync carbs with. It was a little spendy but has paid for itself in my business

Digital all the way and I can tell engine condition in dyn mode

----- Gimpster -----

 

[Gimpster]

dude,

I'd just pull the whole works and send it to gimp and be done with it

Or bring the whole bike here...LOL

----- Gimpster -----

 

[Gimpster]

Here is a carb breakdown for you

http://www.ronniesmailorder.com/fic...ry=Motorcycles&make=Yamaha&year=1986&fveh=161

----- Gimpster -----

 

[xrated]

Thanks for all the ideas fellas,

but seeing all the carb work made me think. I know the carbs just were cleaned last year...So I called him up to verify. Now you can all see how I drank my memory away.

It DOES NOT bog, the problem is that around 6k rpm it has a miss. Other wise it runs fine. This problem developed about midway through last summer.

We suspect plug wires have a part in this so we are gonna jerk the tank and seat and take a look.

does this sound right or do you have other ideas. Oh and it is an 86.

 

[Weekday Warrior]

my answer doesn't change

 

[Gimpster]

Could still be carb syncronization. If one is out of sunc, the others pull it and it draws more fuel through that carb than the others because the throttle is closed more and the same amount of air is passing through it as ther is the other carbs. It makes that cylinder lay down from ring wash and flooding.
Yamaha CDI's are also good for the rev limiter getting 'soft' over time. Meaning that the more and more it is run up on the rev limiter, the less and less it takes to bump against at lower rpms.
If you suspect a spark issue, I suggest ohming the spark plug caps first. Trace back from there.

----- Gimpster -----

 

[Blu Du]

ya it sounds like you better just bring it to gimp. it's only 450 miles

 

[Gimpster]

ya it sounds like you better just bring it to gimp. it's only 450 miles

LOL, loosen up the shim under buckets to my specs, notch the cam gears and degree the cams to where they should have been set by yamaha. Manual cam chain tentioner to free up the chain lag, little ignition plate remanufacturing and add some toluene.....

Turn that slug into a beauty queen that hums on the side without complaint !

----- Gimpster -----

 

[Killerk]

A carb job is only as good as the person doing it.
Your symptoms do not sound like a big issue, but could definately still be a carb issue.
Whether sync, mis adjustment, missing or misplaced O-ring, etc.
If carbs are gummed up and cleaned, they need to be soaked IMO... Lots of small orifices in carbs, a small amount of build up can cause issues.

 

[Numbnuts918]

As stated above...a good thourough carb cleaning & sync is favorable. Make sure your gas & plugs are new as well. Check both your intake boots before & after the carbs for cracks or leakage. Last resort do a compression check & see if you have a variation between cylinders, one could be going south. Keep us posted.

 

[xrated]

Plan is to check the plugs and wires.

Carbs were cleaned last year so we are gonna forego that for now.

I'll let ya guys know what we find. Hopefully we look this weekend if I can get the old fart away from his Harley.