Xs400 only running on full choke

[Riley McDonald]

hey guys! So brand new to this form and not sure if I'm even doing this right. But I recently picked up a 1980 Yamaha xs400 bobber and the bike runs on full choke but once I put it to half its stalls out. I've cleaned the carbs a few times already and ripped the whole carb apart and have cleaned everything. Here's the kicker tho. When I start it up on full choke with the air filters off and put my hand over the end of the carbs I can take the choke completely off and the bike will sit and idle perfectly. So I'm stumped as to what it might be. Thoughts? Thanks guys!

 

[16VGTIDave]

Sounds like you have vacuum leaks to find! Propane, or carb cleaner, or spray lube can all be used to find the leak. Start at the head and work towards the carb inlets. The carb holders are often the problem, but it is difficult to diagnose from a distance...

Good luck!

 

[Riley McDonald]

Sounds good! I will give it a shot, thanks! It also has those pod mounted air filters on it, im assuming its a cheaper one just by looking at pictures of them but have heard there not the best set up to have on the bike. Ive heard the best is to just run the oem H with the oem filters but the pods sit really close to the battery box so i dont the oem would fit. any suggestions?

 

[16VGTIDave]

There are plenty of threads (recently!) discussing pods and why not to use them. Since your bike has been modified, you may need to get creative. Put some tunes on, grab a chair, note pad, pencil, tape measure, beverage, and have a good long stare at the bike. Sketch the current install, then start sketching possible solutions. The creativity will start when you stop thinking about the problem. This is one of my favorite ways to spend an evening.

 

[Riley McDonald]

Thanks for the help!!

 

[Riley McDonald]

I seen you made you own H pipe! Im thinking thats what im going to have to do so the pods arent directly mounted to the carb and get myself some good filters

 

[ensoroni]

Sounds good! I will give it a shot, thanks! It also has those pod mounted air filters on it, im assuming its a cheaper one just by looking at pictures of them but have heard there not the best set up to have on the bike. Ive heard the best is to just run the oem H with the oem filters but the pods sit really close to the battery box so i dont the oem would fit. any suggestions?

Careful with the pod filters. If you have the emgos the inside lip will block some of the air - ports in the carb. mikes XS has some good pods for this. That's the only product I would recommend from him that is XS specific

 

[Riley McDonald]

ok, I ordered myself some double stage uni pod filters