So I'm assuming you've checked for spark and fuel? Does the header heat up when given throttle?
This is a discussion on CB400T Shitbox Build - Daily Driver within the Project Builds forums, part of the Caferacer.net Forums category; So, Question for the group: I'm a little bit stuck on tuning this bike up. The right side header is getting much hotter than the ...
So, Question for the group:
I'm a little bit stuck on tuning this bike up. The right side header is getting much hotter than the left, at idle. After reading about it tonight it sounds like i need to check the carb sync. Here's what I've done...
1. I put a new airfilter in the air box.
2. I refit the rubber air box boots to the carbs and ensured a good seat on both the box and carbs.
3. I replaced the o-ring between the carb boots and the head
4. I bought OEM exhaust gaskets and put the old crusty (and super tight) clamps back on (the aftermarket ones are as worthless as they are shiny).
The only link in the intake/exhaust chain I haven't replaced is the copper ring between the header and head.
I don't know if I need to make any changes now, or wait until I can get it out and ride it at operating temp for longer than 5 minutes. I haven't gotten it registered yet, so I can't know how it runs on the street just yet.
I think for now I'm going to focus on getting it registered and driving around. Maybe the temp issue will solve itself.
Exchange anything you can from the left side to the right side and test, if you can make the problem switch sides you found a problem ?
The left side header gets hot when I throttle up, yes. But not nearly as hot as the right. Haven’t been able to really run it with the throttle open yet. I’m in a basement/bomb shelter with a tiny window, so the fumes go up into the apartment building and people get pissed.
Bike should be coming out next week though
On way to check for a partially plugged idle jet is to introduce some propane and see if that cylinder catches up to the other one. Easiest way is to pull back the boot between the air box and carb or remove the air box. Take a small propane torch and hold the tip close to the mouth of the offending carb. When the bike is idling, crack open the valve slightly. Continue to open it a bit and see if the idle picks up noticeably. Probably best if you do it outside. If heat is uneven, and spark is ok, valves and valve clearance are ok, then its like the man said... a plugged jet or sync is out of whack.
"Non urinat in ventum"
So I think I’ve come up with a solution to a few issues. Firstly, evacuating the exhaust from the basement. I picked up some dryer ducting from the hardware store. I zip tied them to the grate covering the window. The ducting slips over the mufflers and works pretty well!! I ran the bike at 3k for about 30 sec. And repeated about 3 times. I came out much better for it, as the wife will tell you. Meaning I didn’t come home smelling like I just took a bath in gasoline.
Now I need to take a fan down before I sync the carbs, to keep the motor from overheating. Speaking of which, I bought some tubing to make my own manometer. I’ve attached a photo of what I think is the vacuum port on the head side? Am i correct here? I have looked at buying some motion pro brass vacuum tubes, just to do the sync.
I also decided to convert the fuse box over from glass to blade, which is pretty straightforward. The fuse block is like $8 and then it’s jus wiring it up. I’ll probably salvage the harness end of the old fuse block and reuse it.
Also, the Tachometer has started to whine when I rev the bike up. I just replaced the old rusted out tach cable with an OEM one. This happened on an F-250 I rebuilt, which preceded the needle popping off of it the gauge entirely haha. So I’m taking that as a sign that I need to hunt down new gauges.
Last edited by jakejensen; 02-28-2019 at 02:25 PM.