Fuel Issue or Not!!!

[roadrunner]

Hi there,
My bike bogs down when i try to open her up, i have tried every trick in the book but nothing seems to do any good. :? This bike had a Boyer Bransden Electronic Ignition fitted, so what we done is put it back to the points system to see if that did any better, but no.
Carbs ok, ignition ok the thing is that she will red line sitting in neutral but will refuse to open up when under load!!!
Looking for any suggestions info etc, etc etc[-o<


Full history under "GS Underpowered"

[Nicholaschase29]

like I said on your other thread

"i would guess that you have to rejet your carbs. do you have individual air filters and aftermarket exhaust? if so and you have never rejetted you will probobly be running to lean at 3/4 to full throttle. mabey try to pull the plugs out after you run it where it boggs the most for like 1-2 minutes and see what color they are...."

[roadrunner]

Hi there,
only 1 air box for all the carbs, and i have a 4 in 1 exhaust fitted, original jets etc no modifications at all.

This ia a GS550ET (V) plate 1980
Any reason for it bogging down under load?
:?

[RoyalFlush10]

if you have a 4-1 kit on you are going to need to run a jet kit on it. Probably a stage 3 kit.

Should run you about $100 - $130 shipped.

[Mike McNaney]

Hi guy's. This guys problem reads like a made for TV movie!

I'll be the first to admit I havent seen alot of drivability problems on bikes. But I have seen them ALL on Cars.
Semi -the same Ive found working on my bikes.

Your vacuum gauge is telling you something. I didnt see milage anywere but inches of vacuum is not a symptom of fuel delivery. Low vacuum can make the problem worse by not operating the petcock properly but I think The problem is timing/ignition. Id step out on a limb and throw up that if it was a car, Id check to see if one cam is one tooth off.

Also, come to think of it, maybe with the vacuum guages attached, try moving the point/pickup plate to see if it will advance until vacuum goes up to 12-14 at idle, if so.........

Does this have points? high dwell / point float will cause no high rpm capability also.

Timing also makes sense when you say that it sometimes wont even start when you know its getting gas and spark.

[Dave8338]

I have to agree with mike on this one...double check the timing, also jets will most likely be needed with the 4-1 pipes.

[8trackmind]

It has CV carbs right? if so, it's not a fuel problem. It's a airbox leak. The boots going from the airbox to the carbs to be exact. (one, or both of the two in the center most likley)
If the leak is large enough, the bike WILL NOT run over 4,500 rpm under load. It'll go rich and look like a fuel problem. (black plugs)

Btw, a CV equiped 550 with stock jetting, stock filter and airbox will run just fine with a 4 into 1.

So, what do I win for solving you're problem?

[Mike McNaney]

Heres a chance to share a tip on re jetting after header install.

A rejetting issue after header install will be a lag in accerleration. It will reach a point were acceleration slows down from its previous intensity but still accelerating. It'll get there, just not as fast. You wont get a rpm were it wont pass.
About 5 #'s is what a header change is worth. Not really very much. On my bike, a 83' 1100E, stocks are 112's. After header install it needed 117's and then after pod filter install 122's. (which by the way is stock for an 1150 motor) Then later, I went to 1166 cc and 36mm carbs and it went to 150's

If you like to fiddle with things, heres how I did it.
I had a stock motor torn down and when put back together it was a larger displacement, compression ratio, different carbs and 4/1 header

I have BS Mikunis and you can take the mains out with the carbs in place by draining and removing the fuel bowls. I took out one jet, went to a good tool store and found a drill bit the exact size. Then I bought 10 bits the next sizes up in 128ths. $2ea.
Opened up the jets until the upper end bog went away. Each change was noticable on the tach as I accelerated. Then I found the actual size number jet that represented the size I and found it was a 150 size, bought 4. $5ea. High retail.
The pilot jets are fine unless you are going to do be doing alot of on/off throttle stuff (Racing in the twisties)
Oversize pilots dump more gas in transition. off throttle / on throttle, idle / mid / WOT.

Now in this story I had a drill press, appropriate short screw drivers, a means to drain the float bowls without making a mess, a freind in the parts/service dept at my local suzuki dealer and a new set of float bowl gaskets.

[Mike McNaney]

Whoo Hooo for 8 track. If thats it. It would be a huge relief!!

[roadrunner]

A stage 3 jet kit!!!
What does that involve, as i have mentioned earlier no mod cons apart from the 4 in 1 exhaust.
Could you give me the address of a good supplier of jet kit that i require.

Also we will be checking to see if the cam chain has jumped a cog or two, maybe this might be the solution or maybe i am not getting a good seal from the airbox to the carbs!
Anyway i will stll be trying any suggestions possible.
This is a GS550ET 1980 V plate with 44000 miles.

Cheers

[chef1366]

http://www.dynojet.com/jetkits/motorcycle/suzuki.aspx