Good report, but where to begin...

So..... I got home a little early and synced the carbs. It took a minute, but I finally got it to idle alright. Took it for a test run and it ran HORRIBLE. I pulled over and tried adjusting the air mixture screws.... finally said "screw this", and rode it home to work on it. When I got home carb 1 started spitting a little bit of gas. Pulled the float bowl, and replaced the float. Looked like the po did a prior repair on a few of them. I've been skeptical about the fuel filter, so I took it off too. Bolted it all back up, and readjusted the screws. Fired it up, and adjusted until it idled good. This time I ended up at 2 and 1/2 turns. Ran pretty dang good.

A little bit of popping at times, but nothing serious. Ran great through all rpms.

The only thing that concerns me is one pipe, #4, is much cooler than the other 2. 1 plug, #1, is turning black. Any ideas how to tune from here?


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1 and 4 run off the same coil so you might have ignition related issues as well.


Check the ignition pick-ups are the correct distance from the rotor - this is often overlooked and can cause poor spark which can seem like a fuelling issue.
 
I found information on the gap, and I'll give it a look. I've checked the timing and it looks perfect. The only reason i would doubt that theory is plug 1 is black and plug 4 is clean. Could it be a valve issue?


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Also, I haven't done a proper plug chop, so you may have nailed it


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88SS said:
Well..... while tightening the cam chain, I totally broke the bolt off. Will this still be ok to ride with until I can replace it?


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There are two cam chains. If the bolt you broke off is the one next to exhaust pipes, no worries. The other adjuster is underneath carbs in middle of block. It's usually worthless to try adjusting without cam cover off so you can check tensioner moves (or push it down a little if it's stuck)
Tapping is probably loose intake shims, the exhausts tend to tighten up and burn valves if adjustment isn't done.
750 is 'nicer' motor than 900, the shorter block/cam chain doesn't destroy itself as quick
 
I actually had someone tell me the same exact thing at a swap meet. What are the symptoms for a burnt valve? I've had a mixed bag of opinions thrown my way on the valves. Some say don't mess with them, and some say they need to be adjusted.


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You will have hard starting when tappets are too tight but bike will seem fine when its hot as the cam 'moves' away from valve stem when head expands. I would pull cover and check clearances. Shims are easy enough to change, no idea why anyone would say don't mess with them? If you find any tight (I mean zero clearance but just about able to turn bucket) go at least 0.001" thinner than needed on shim. It's a good idea to mic them as the etched numbers are often 'closest to' and not exact 270, 275, etc (actual thickness in millimeters, 2.70, 2.75, etc) 0.05mm is a bit less than 0.002" (I'm British and brought up with inch and metric systems late 60's- early 70's)
I used to have shim kits for 'everything' but that was mid 80's. It's possible to change shim without special bucket depressor, have cam lobe pointing up in line with the valve, pry bucket down with a screwdriver then use a piece of 1/8" bar curved to fit cam on the two buckets
 
That's good stuff crazypj. Thanks man.

I took it on a 100 mile ride today. It ran pretty good. Not perfect, but acceptable. It fired right up, but sputtered for about 10-15 minutes. Took me a good 20-25 minutes to get it warmed up. Once I got it down the road a way, it idled ok. Would sometimes rev to like 2 thousand rpms, and sometimes it would drop down below 1,000. So, I'm almost there. Tomorrow I'm going to try another 1/4 turn on the mix screws and see what happens. I need to definitely shim the valves. I'm thinking the slide needles are non adjustable. They don't have a clip.


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Almost forgot, you need larger pilot jets but not by much. Bike came very lean from factory, check various 'overseas' models to find the largest ones fitted (can't remember if it was Australia or Middle East?)
You should alo check the 'air cut valves' on sides of carbs, pretty sure your year has them?
You should also have accelerator pump, check diaphragm, they are almost alays busted.
The accelerator pump linkage is a nightmare to fix if anyone has taken it apart
 
crazypj said:
Almost forgot, you need larger pilot jets but not by much. Bike came very lean from factory, check various 'overseas' models to find the largest ones fitted (can't remember if it was Australia or Middle East?)
You should alo check the 'air cut valves' on sides of carbs, pretty sure your year has them?
You should also have accelerator pump, check diaphragm, they are almost alays busted.
The accelerator pump linkage is a nightmare to fix if anyone has taken it apart

My accelerator pump was definitely busted. I changed it out. I haven't broken the carbs all the way apart, separating the banks, so I haven't changed the air cut offs, but I do have the replacements.

I think stock is 68/102, and 68/100 was on the bike when I bought it. I jetted to 68/105, and that didn't work so I'm now at 70/102. I think it's pretty dang close. I'm not entirely sure what the air cut offs even do. Would it make a huge difference to change them? How does it run if they are bad?


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You have what are known as 3 jet carbs. The pilot jets are either fed from primary main jets (68~70) or are pressed in brass tubes.
They will be around 35~40 but may not be marked The easiest fix is to get hold of a miniature pin vice and sub miniature drill bits. I have 0.30mm and 0.35mm (around 0.012") A jump of 0.05 is pretty major if you work out increased area for fuel flow
If I remember I'll dig manual out tomorrow and see if I made any notes in it (plus I can have a fresh look at carbs)
 
crazypj said:
You have what are known as 3 jet carbs. The pilot jets are either fed from primary main jets (68~70) or are pressed in brass tubes.
They will be around 35~40 but may not be marked The easiest fix is to get hold of a miniature pin vice and sub miniature drill bits. I have 0.30mm and 0.35mm (around 0.012") A jump of 0.05 is pretty major if you work out increased area for fuel flow
If I remember I'll dig manual out tomorrow and see if I made any notes in it (plus I can have a fresh look at carbs)


Pretty sure mine are pressed in. I could be wrong. I haven't tried to get in after them


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Man you've been through it! I had a lot of similar problems with my dohc. Header 2 running cooler, running lean, can't find sweet spot in air/fuel screws, running rough, fooled plugs,... I replaced plugs, coils, carbs, had the valve lash set at a shop but nothing worked. I believe my problems are from bad rings, low compression. I have 65-75 per cylinder. What are your compression numbers in each cylinder? Have you done a leak down test? I'm rebuilding mine with a Wiseco big bore kit haven't put it back together yet. I run the Mikuni 2 into 4 carb kit from speedmotoco. That's the budget friendly way to replace carbs on these bikes. I saw a newer kit with 4 Mikunis as well. I think with the increase in price on the CRs that makes a lot of sense.

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phparray said:
Man you've been through it! I had a lot of similar problems with my dohc. Header 2 running cooler, running lean, can't find sweet spot in air/fuel screws, running rough, fooled plugs,... I replaced plugs, coils, carbs, had the valve lash set at a shop but nothing worked. I believe my problems are from bad rings, low compression. I have 65-75 per cylinder. What are your compression numbers in each cylinder? Have you done a leak down test? I'm rebuilding mine with a Wiseco big bore kit haven't put it back together yet. I run the Mikuni 2 into 4 carb kit from speedmotoco. That's the budget friendly way to replace carbs on these bikes. I saw a newer kit with 4 Mikunis as well. I think with the increase in price on the CRs that makes a lot of sense.

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I haven't put a gauge on it yet to check the compression. It fires right up, and only has 20,000 miles on it so I assumed it was passable. The plan was to ride it this summer then break it apart this winter, so good enough will work for now. I've been looking into the mikuni setup. I'm really going for a restoration, but it seems like the carbs need an upgrade. They are kind of a pain.

While I'm on the subject, does anyone specialize in restoring paint? My tank needs some love


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May have spoke too soon. Hard starting today....


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It took a while to get it fired up, but she was running like a champ. Pretty sure the choke is out of adjustment again, but I may be wrong. I have a hard time believing it would run that good if it were more serious, but maybe I'm wrong....

It was cold and pouring but I just couldn't stop riding. Came home soaking wet with a big ol smile on my face. Fingers crossed it's the choke again.


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4e08ad892f12f3b0fa6ec0aa7963f4dd.jpg


It was definitely the clutch. I made a slight adjustment on the cable, and it fired first try. Took her for a long ride today. A little chilly, but I didn't mind. It was just good to be on the road


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Anyone know how to wire the rear blinkers. Bought a set of two wire blinkers, and for the life of me I can't get them to work. Something isn't right


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If they are less than 21w you will need some resistors or a new flasher relay.
If they are LED, you must have live and ground on the correct terminals. What colour are the wires coming out of new indicators?
 
The flashers just have a power and a ground wire. I'm pretty sure I hooked them up correctly. Buuuut they didn't turn on. One of the POs have been in here doing some wiring. I'm assuming for lights on their touring racks.

The relay has two plugs that are connected then a green wire that comes off, that isn't connected. Also, it looks like a wire has been snipped on the hand controls.

I'm thinking the problem is going to be slightly more complicated than a simple replacement


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