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defective 400A carb insulators

redlotus

Veteran Member
Joined
Jun 28, 2022
Total Posts
125
Total likes
22
Location
Columbus, OH USA
Hi guys. After I had the carbs rebuilt, replaced a plugged petcock, cleaned the tank, and bought new insulators for my '81 400A I thought I'd be all ready to go.
But it ran like * and turns out a spray test revealed that the new insulators with new O rings are leaking at both the head and the carbs! WTH :( I followed a link to a place in Japan called cruzinimage someone here suggested recently, tho don't remember what thread. They seemed to fit fine and were supposed to fit '78 to '82 400A's. Anyone know this firm? Also perhaps a better source for another pair? Might be some other problems with the poor running but got to get those leaks fixed before anything else. Maybe a temp fix with a bunch of silicone? Not :) I was hoping to get this on the road before the snow flies. New plugs, battery, 14 + volts at the battery with some revs. Thanks for any input. Cheers, Ron
 
The only thing I've seen others have experience with buying from Cruzin Image was piston sets and until recently, reported with good results, but I've never personally bought from them nor have I heard anyone else mention buying anything like carb boots from them either. Sadly, there are many cheap knockoff carb boots out there and the 400A is apparently really hard to find boots for.

I did a little searching and found these, pricey but OEM

https://www.davidsilverspares.com/parts/by-part-number/partnumber_27229/
 
I was the one that suggested Cruzin Image, their pistons have been good for everyone so the assumption was the insulators should be good.
You might want to email them and advise them of the problems.
When you say the leaks were at the head and carbs did you check the insulators to see why? Is the head mount plate warped/distorted? How tight is the fit of them onto the carbs? I know some insulators from Honda are really hard to get the carbs fully inserted to where the carb and insulator almost bottom out on each other.
 
Thanks guys. I'll pull the carbs back off and double check orientation. Maybe they aren't parallel. Don't recall any marks on the old or new to help with that. Might just put the old ones back on with new O rings. They were a * to get off tho. Didn't someone suggest a soak in winter green oil to soften mounts and boots? Sounds like something you'd get in what we used to call "head shops" - and not the kind that involved milling machines :)
 
Yes, people do use wintergreen oil to soften rubber parts, insulators in particular.
Speaking of orientation the old insulators will have an arrow on the carb lip and maybe the replacements have that as well.
201_4035-001.jpg
 
No marks on the new ones but I'm pretty sure I had them installed correctly. I reinstalled the old mounts with new rings, and while they seal much better, they still leak with a spray test and it won't take much throttle, and rev limited, so no luck there. I guess I'll contact David Silver for another pair, tho that part no wasn't recognized. I'll look later. I need to move on and think I'm going to take Bill H's kind offer to sort it out for me. So some luck there - 90 min away :) Meanwhile I can work on finishing my '71 BMW 2002, Minis and scooters I know more about :) Thanks again for the input. Cheers, Ron
 
If you trying to make the carbs work w/o the air box connected then this sounds pretty normal

At one point it was all hooked up and maybe ran slightly better, but still way off. I'm curious to see how it'll run with good mounts on it and will order a factory pair I guess. No word from Cruzin.
 
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