Author Topic: Carbs..... please help!! (Read 3659 times)

weltzing · « **on:** August 02, 2012, 08:39:24 PM »

I have a 1980 cb650c and I just completely went through my carbs and put new o-rings, accelerator pump, and air cut off valves in. I also bought new carb insulators. My question is why are the carbs offset from the head. Either the 1 & 3 carbs line up with the head and the 3 & 4 are off a bit OR the 2 & 4 line up and the 1 & 3 are off. I wrestled them on the head and the straight boots are at an angle. WHY is this?? Doesn't make sense to me because the boots are straight. Everything is stock so why is this?

PLease, please help!

trueblue · « **Reply #1 on:** August 03, 2012, 01:53:46 AM »

Make sure you have your insulators installed with the arrows to the top and pointing to the engine. The boots are slightly off set and if they aren't installed like this they won't line up.

weltzing · « **Reply #2 on:** August 03, 2012, 10:51:31 AM »

I made sure the arrows are on top, the offset of the carbs to the head is more than slightly. the isolators are from the honda dealer and have the number 460 on them with an arrow

trueblue · « **Reply #3 on:** August 03, 2012, 05:27:22 PM »

The carbs you are fitting came off this engine? There are 2 different types of carbs for the 650 and they don't interchange. Failing that post some pics, so we know what you are looking at.

weltzing · « **Reply #4 on:** August 03, 2012, 05:36:37 PM »

I'll try to get some pics, but these are the slide type carbs PD's. I actually got a spare set from a guy on here that had the same bike and used some parts from his...

trueblue · « **Reply #5 on:** August 03, 2012, 05:55:35 PM »

Ok, an 80 should take PD's, I'm assuming you removed PD's from the bike. If you did then a carb mix-up shouldn't be your problem.
But if you didn't remove the carbs, it is possible that someone has either fitted a later head, or engine to your bike and you may need CV type carbs.

weltzing · « **Reply #6 on:** August 03, 2012, 06:21:10 PM »

If someone else has a picture of their cb650c please post one of their carbs mounted to the head!.....I'm the second owner and the previous owner had the bike parked in his shed for 10+ years before i bought it..I'm am almost 99% sure everything is stock.....Ever since i bought it 5 years ago I have had problems with the carbs. The carb insulators never fit very good and always at an angle so the clamp never sealed the boots very well. I finally had enough time and money to get new carb insulators, air cut offs, accelerator pump, float valves and so on. Now that all carbs have been gone through, new needle valves, floats set to specs, everything is in order now. Still the isolators still are angled.........

weltzing · « **Reply #7 on:** August 03, 2012, 07:54:04 PM »

I'm having problems trying to attach photos, not sure if I'm doing it correctly, is there an easier way?

scottly · « **Reply #8 on:** August 03, 2012, 08:19:41 PM »

Total size per post is 1 meg. Downsize the pics, or spread them out over several posts.

weltzing · « **Reply #9 on:** August 03, 2012, 09:32:47 PM »

Hmmm and how do I do such a thing? pic says its 1.94 mb

trueblue · « **Reply #10 on:** August 04, 2012, 01:20:40 AM »

You can down size them in paint

, failing that you can use photbucket, it's free to start an account. If you can measure the ports on your head from centre to centre of 1-2 and 2-3, 3-4 should be the same as 1-2. I have both types of head here without carbs on them and I can tell you which one you have and what carbs are supposed to be on there.

Hush · « **Reply #11 on:** August 04, 2012, 01:41:27 AM »

Here is a picture of two sets of carb isolators both off a 79 CB650Z with PD carbs, hope it helps.
The off-set is not that much on the pd carbs but you do need to get those arrows lined up right.
I had trouble getting my 650 tuned right, took it to a mechanic in the end and he found that I had not pushed the carb bank on all the way, it looked right but was leaking air.

trueblue · « **Reply #12 on:** August 04, 2012, 02:38:14 AM »

I just went and did some quick measurements, the CV carb head from 1-2 and 3-4 is 65mm, in between 2-3 it is 92mm. The PD carb head the measurements for 1-2 and 3-4 are 76mm, and 2-3 is 81mm. These measurements are centre to centre.

weltzing · « **Reply #13 on:** August 04, 2012, 07:07:32 AM »

heres what it looks like

JimJamerino · « **Reply #14 on:** August 04, 2012, 10:00:20 PM »

That's not right. The boots on my 1980 CB650C are a straight shot from carb to head.

trueblue · « **Reply #15 on:** August 05, 2012, 02:45:14 AM »

Something funny going on there. The boots on my 650Z with PD's and my 650SC with CV's are both a straight shot at the head. The carb boots on both are slightly off centre, but when the arrows are at the top all the offset means is there is a slight drop from the carbs to the heads. Measure the carbs and compare them to the head using the method I mentioned before or take the boots out of the way and hold the carbs up to the ports on the head, they should line up. There shouldn't be more than a couple of millimetres difference between the carbs and head.

weltzing · « **Reply #16 on:** August 05, 2012, 05:57:03 PM »

When I had the carbs off before I remeber that the spacing between the head ports of 1 & 2 and then 3 &4...The spacing between 2 & 3 on the head is different from the spacing of the rack of carbs between 2 & 3..That is why all the insulators have to be angled to make up the difference between 2 & 3 from the rack to the head............Does anyone know why?
thanks

Hush · « **Reply #17 on:** August 05, 2012, 11:46:00 PM »

Could it possibly be that a PO has used a CV rack to sit PD carbs on?
That's all I can think has happened, PD carbs fit straight on, and if the head was for CV carbs it would have wider not narrower spacings!
So I'm saying Early model 650 head, CV rack, PD carbs.....why would anyone do that?

trueblue · « **Reply #18 on:** August 06, 2012, 04:03:32 AM »

You can't re-rack the PD's with CV spacing, not without serious work. I just had a brainwave, I lined up a set of CV carb bodies I have and a PD carb head, and the difference is much the same as your carbs and head. I am certain you have the later model CV carb head with the earlier carbs. The spiggots on the head are the same size for both carbs so you the boots will fit either head. I'm going to be using later model boots on my 650Z when I change my carbs to 32mm mikuni CV carbs.

weltzing · « **Reply #19 on:** August 06, 2012, 03:26:44 PM »

So you're telling me that I should have CV carbs on my bike? F^@#, I seriously just spent 2 weeks and $150+ on getting my carbs ready with new parts and setting to spec....So, is there a for certain way of telling instead of just measuring? Like, is there a number or letter stamped into the head at all? Also is there a different style head on it as far as valve covers for CV and PD carbs?

weltzing · « **Reply #20 on:** August 06, 2012, 07:16:45 PM »

I just looked for some numbers on the head and what I found so far was # 1211 which was in between the 2 & 3 ports on the head. Does this identify anything?

trueblue · « **Reply #21 on:** August 07, 2012, 02:07:49 AM »

The only way to know for certain is measure your port spacing, the 79 650 had "OHC 650" on the tappet covers but these are interchangeable with the later smooth ones. The 80 had smooth tappet covers and PD carbs. I checked all 3 of my heads and none of them have any identifying numbers that would be any use on them. I'm sorry to tell you but I think you will need to get a set of CV's. The only way for certain is to check the spacing, the measuremnts are in reply 12. When you're looking at the ports the CV carb head has a significantly wider gap between 2-3 than 1-2 and 3-4. Whereas the PD carb head the ports are more or less even spacing.

weltzing · « **Reply #22 on:** August 08, 2012, 04:59:35 PM »

The bike is a 1980, had PD carbs, and smooth tappet covers. I wouldn't think the PO would swap out a motor and use the old carbs for it. Or I wouldn't think he just swapped out the heads either...I might try to look up the PO which is the guy on the original title and ask him some questions and see if he infact did switch something out....I actually bought the bike from a neighbor guy who just stored it in his garage after he bought it from the original owner.

lucky · « **Reply #23 on:** August 08, 2012, 06:31:40 PM »

Quote from: weltzing on August 03, 2012, 09:32:47 PM

Hmmm and how do I do such a thing? pic says its 1.94 mb

Do you have
Photoshop?

All the IBM computer people really need a program to downsize photos.
A simple program.

weltzing · « **Reply #24 on:** August 08, 2012, 07:31:15 PM »

No I do not have photo shop, but i did as the other guy said, used paint and downsized it and posted a pic earlier.

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Author Topic: Carbs..... please help!! (Read 3659 times)