High Idle problem solved! One last issue that came up!

[VermontNewbie]

Now this is on my Yamaha 700 Maxim, but its air cooled 4 cyl just like the bigger GS bikes, wondering if I can get any insight into this.

The bike starts beautifull at a push of the button idles and runs. It runs beautifully until it gets hot. When the bike is hot it refuses to idle, it will start if I HOLD the ignition down and crank the gas, then it will idle at 1000 for a while and rev up like everythings fine, but if I get it into idle range it will bog down or stall until I crank the gas and then it will rev up. Now the tank has a significant rust issue, and this is getting sent out for restoration soon. I don't believe the rust to be an issue because after it cools down in my garage it starts and runs like before so the pilot jets must be fine. Any takers? One last little nugget of info here is my plugs read a tiny bit rich.

[Anonymous]

Re: High Idle problem solved! One last issue that came up!

Now this is on my Yamaha 700 Maxim, but its air cooled 4 cyl just like the bigger GS bikes, wondering if I can get any insight into this.

The bike starts beautifull at a push of the button idles and runs. It runs beautifully until it gets hot. When the bike is hot it refuses to idle, it will start if I HOLD the ignition down and crank the gas, then it will idle at 1000 for a while and rev up like everythings fine, but if I get it into idle range it will bog down or stall until I crank the gas and then it will rev up. Now the tank has a significant rust issue, and this is getting sent out for restoration soon. I don't believe the rust to be an issue because after it cools down in my garage it starts and runs like before so the pilot jets must be fine. Any takers? One last little nugget of info here is my plugs read a tiny bit rich.

No doubt in a couple hours the gurus will reply and make my post irrelevant but I'll give it a shot.

From what I gather:

Issues that appear only when an engine is hot tend to be ignition-related and not carb related. You might find something interesting if you check your sparks both when the engine is running well and when it is having the problem.

But again, I really don't know so it's only worth what somebody will buy it for.

[VermontNewbie]

I believe the ignition to be fine as the bike can rev up, just not idle.

[Anonymous]

I had a similar problem with my gs550. I found out that i had 3 bent valves Try a compression test.

[VermontNewbie]

Is there any other way to check for bent valves besides popping them out and a compression test? It's not too hard because its a shim overbucket, but I dont have any way to do a compression test thats you know.. cheap

[Anonymous]

i know a vrey cheap way to do a compresion test....surely there's an auto parts store nearby, many of which will loan out testers for a deposit, you pay the deposit on the tool, pull your plugs, check and record your compression, take the tool back, get refunded, hop back on the gsr site and let'em know what your comp. test reads, several upon many of the ladies and gents on this site will know what the compression should be....i myself have no clue what-so-ever

Just giving you advice on what I'd do


Steve

[SqDancerLynn1]

MAKE sure to hold the throdle all the way open when doing a compression test. Should be 120 -160 lbs depending on engine and cams

[Dark Jedi]

I wonder if your intake boots are maybe FUBAR. They get softer when hot, meybe the extra flex lets them seperate from the engine mounts, leaking in air?

[robinjo]

MAKE sure to hold the throdle all the way open when doing a compression test. Should be 120 -160 lbs depending on engine and cams

Would more agressive cams give a higher compression ratio reading?

(Sorry to get off-topic in your topic, just curious )

[Anonymous]

MAKE sure to hold the throdle all the way open when doing a compression test. Should be 120 -160 lbs depending on engine and cams

Would more agressive cams give a higher compression ratio reading?

(Sorry to get off-topic in your topic, just curious )

It's bben my experience that they give a lower compression reading - given that everything else is the same. This is becuase they have more overlap.