Need Advice-possible fuel/carb problem

[Guest]

Hi. I have a 78 GS750. My bike is starting hard and getting harder. After getting it started I have to hold the throttle on. The throttle response is not good at this point. If I can get it to rev hard up to 5000 rpms it feels like something pops and then it idles fine and off I go. Unfortunately this problem got worse today and it takes 3 or 4 start attempts to get going. Once I've been riding the bike for a ways it seems to even out and ride fine but I'm worried it's getting worse. I took off the tank and petcock and everything looked fine there but it ran worse after. Not sure if there's a connection there. any advice would help.

[tom203]

What maintenance have you done ? Sounds like carbs, but lots of potential for other stuff.

".....I took off the tank and petcock and everything looked fine there but it ran worse after. "
Maybe a coincidence, but did you check flow of petcock? Still got a vacuum operated petcock?

seen this link?

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

[Steve]

How long have you had the bike? In other words, is this something that has been developing over a long time or is it a 'new' bike to you and you just realized that it's not all that the seller promised?

Have you done any of the required maintenance? Carbs cleaned/rebuilt? Valves adjusted? Dirty carbs and tight valves are classic signs of hard starting. Dirty carbs are a classic sign of poor running after it does get started.

.

[rotten ron]

I have had the bike about 7 months or so. The seller didn't know much about maintenance history. A friend and I gave it a tune up shortly after I got it (took off carbs and cleaned them, checked valve clearance, timing, adjusted idle and air screws). Everything I've seen taken apart on this bike looks in great shape. Ran great for quite awhile then started showing symptoms of this problem .Shortly after I mistakenly put way too much oil on the air filter after cleaning it. The plugs fouled. I replaced the air filter and plugs and sprayed carb cleaner in the air intake ports of the carbs until it felt clear and good and off I went. Still the problem came back. I'd think it was just a carb recleaning issue but it was starting to happen with squeaky clean carbs. One of the valve clearances was very slightly off and could use a shim but It seems very hard to do on this bike so haven't done it. Thought about checking for vacuum leaks with a can of carb cleaner sprayed on spots while the engine is running. Just need to know where to start with diagnosing the problem My mechanical skills and tools are limited. I'm learning.

[tom203]

You need to correct valve clearances- they likely have changed from your initial measurements, especially if bike sat idle before you arrived (you might have got false readings). Join the shim club here to exchange shims. Head to this link

http://members.dslextreme.com/users/bikecliff/images/gs850valve_adjust.pdf

at bottom of Steve's post, note valve spreadsheet offer

[Big T]

Hard starting is generally tight valves

Did you replace the points and condensors?

Sounds like you need a full maintenance

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