Engine problems

[estagor]

I just came back from a ride and I had a knocking sound coming from the engine. During my ride low power with engine bogging down in 1 st and 2nd gear. I came right home, felt the exhaust pipes and 1 and 2 very hot but 3 and 4 warm enough that I could put my hand on them and hold them... I have 1981 GSX750....I think I've got a huge problem......

Any comments.....

[psyguy]

a bit more history would help diagnostics

i would start by confirming that you have a good spark on cyl 3 and 4 (cracked wires, old plug caps, bad sparkplugs)
if that's all good, check valve clearances and do a compression test - that should tell you about the general health of the top end
finally, knocking... usually related to conecting rod bearings failure (bad) but in itself i doubt it would cause cylinders not to fire

ps. could be the dirty carbs too, so as the list of suspects grows, you need to start eliminating some of them

[SqDancerLynn1]

I would start by checking the valve adjustment, then clean the carbs, Check the oil pressure...

[estagor]

Thanks for the feedback and I will be providing an update on the trouble shooting suggestions

Gord

[psyguy]

Thanks for the feedback and I will be providing an update on the trouble shooting suggestions

Gord

in case you havent seen this yet
a list of common issues on gs's

http://members.dslextreme.com/users/bikecliff/images/GSR_Greeting.html

[estagor]

I pulled all the plugs 1 and 2 black with carbon build-up, 3/4 not bad. I replaced them and within 150km same results blackened ..etc..I did a compression test on all cylinders and there running a 130 psi across the board. Carbs were rebuilt last year by my mechanic and he feels that there not the problem. I replaced the air filter and oil change just for kicks and will verify if the bike is running to rich this week (waiting on the tool from Suzuki) I was told to look closely at the ignition coils and test them by swapping sides to see if the problem follows. If the problem follows I was recommended to buy aftermaket coils any comments on a brand?? Dyna?

[Skyboy8950]

Tool? Suzuki? Check to see if it is rich? Explain...

[SqDancerLynn1]

One bad tank of gas can clog the carbs so don't go by what your mechanic says. Dyna 3 coils work great. Check and make sure you have 12 volts on the coil. Could have weak spark. Is the bike stock ? rejetted ???

[psyguy]

as i said, you need to starte eliminating suspects
compression is good so thats not your prob
you still need to check the valve adjustment
by all means check the voltage to the coils but the coils themselves rarely fail in a way to give you your symptoms
yes, you can swap the coils to see if the problem follows, but i bet it wont

[estagor]

I found a reference in my manual on a tool that you can attach to the outer carb's to verify the amount of fuel entering the carb. If it exceeds a defined line it recommends to have the amount gas coming adjusted or regulated. The tool is about $20 Cdn and should be in today. I have the Suzuki part number a home and I will add to this thread.

[estagor]

The bike is 100% stock which these days is getting hard to do but I'm trying. If I got to the after market ignition coils it will be the first part!!! When the carb's were done last year the jets were replaced.

[estagor]

I will be swapping the coils tonight and let you know. At some level this is fun but I want to get back on the bike as the weather here sucks somtimes and I seems to have problem when it's nice outt.. I will get back to ya...thanks again this place is the best for information!!!!!

[jonshep]

I don't know if I fully understand which plugs are black and which ones are clean but cylinders 1 and 4 fire together and 2 and 3 fire together. Usually if 3 and 4 don't fire, ie. cold pipes, that would indicate carb problems. Two are set way to rich and fouling the plugs. How many miles on the machine? Carbs were reworked last year, did they set over the winter? Gasoline is not what it used to be and it don't take long to gum up the works.

[estagor]

It is 1 and 2 that are causing the problems thus why I think the carbs need to be checked but my mechanic wants to change the ignition coils, I had not time last night to verify the voltage of the coils hopefully tonight. In addition I finally received the fuel level gauge from suzuki to verify the float level in my carb's thus I can see if to much fuel is getting into the carb's. The next step is to the verify the valve clearance as mention before.... With respect to having fuel left in the carb's over the winter, I don't think so as I had the tank off for painting and I ran the engine dry to ensure that no gas was left.....in the bike.(the bike was stored in-doors)

[seuadr]

It is 1 and 2 that are causing the problems thus why I think the carbs need to be checked but my mechanic wants to change the ignition coils, I had not time last night to verify the voltage of the coils hopefully tonight. In addition I finally received the fuel level gauge from suzuki to verify the float level in my carb's thus I can see if to much fuel is getting into the carb's. The next step is to the verify the valve clearance as mention before.... With respect to having fuel left in the carb's over the winter, I don't think so as I had the tank off for painting and I ran the engine dry to ensure that no gas was left.....in the bike.(the bike was stored in-doors)

well, it's really simple to see if it's the coils.. swap 1 with 4 and 2 with 3.. if the problem moves with the wires, it's electrical, if not, it's probably the carbs and/or an air leak.