Topic: Lost all compression

[Blue2swing]

I found another person on this forum having the exact same problem I'm having. Everything running perfectly except for quick plug carbon build-up when running cheap aftermarket pods (http://forums.sohc4.net/index.php/topic,122701.0.html).

So what I'm going to try to do is run hotter plugs to help burn off some of the carbon build up ( I bought a 10 pack of NGK-D7ES's on eBay for $23). And swap out my cheap pods for $130  K&N RC-2314 pods. K&N claims their pods resolve problems like this, without the need to adjust the carbs, by allowing greater airflow through their cotton fabric filters.

If that doesn't work then I'll Jet the carbs to increase the air mixture and adjust the bowl gas level to reduce the amount of gas available in the bowls.

I'll update you guys once the K&N pods and NGK D7ES come in and I get them strapped onto the bike.

[PeWe]

NGK D8EA should work fine. It might be floading float levels causing very rich.
Pilot jets 40?
Tried to adjust air screws?
Ignition OK, F align with case mark at idle as well as full advance aligns after 2500rpm? If idle is OK but full advance happen  too early, tighten the adv springs by cutting them 1/2 wound.

[Blue2swing]

NGK D8EA should work fine. It might be floading float levels causing very rich.
Pilot jets 40?
Tried to adjust air screws?
Ignition OK, F align with case mark at idle as well as full advance aligns after 2500rpm? If idle is OK but full advance happen  too early, tighten the adv springs by cutting them 1/2 wound.

I haven't touched the carbs out of intimidation. I feel lucky to have made it this far in my build with the amount of success that Ive had. I was expecting to get nothing from the engine after the rebuild and then have to pass the project on to a professional to have it finished off .

I'll read the manual to look into adjusting the float levels this weekend.

The current jets I believe are stock, so 40 should be correct.

No adjustments has been made to the air screws. I don't know how to work them, so I'll read up on them as well.

The ignition is aligned to the case mark. I did NOT check it with a timing gun at 2500rpm.

I was so happy the first time the bike fired up (my second/third attempt) that I decided to leave everything as is .

FYI - The carbs ran perfectly before the engine rebuild (with the stock air box). I assumed they should be running just as fine after the rebuild if I was careful to not tweak as they sat on the shelf.

I should also point out that the bike sat for 8-9 months before the last ride. It's only got 35 miles on it but I just read that the old gas can also cause additional carbon build up.

[dave500]

lets hope the cheap ngk plugs are genuine.

[Blue2swing]

lets hope the cheap ngk plugs are genuine.

[dave500]

its common,check this.
http://www.ngk-sparkplugs.jp/english/techinfo/fake/index.html

[PeWe]

A good idea to check carbs inside if bike always have been running rich for you. The PO miight have missed to tighten the jets or something simple completely wrong.
Another thing if it has worked OK when you have owned it, you know the status of the carbs.
I shouls remove carbs, open them, remove pilot jet, main jet and the tube it is fasten into (needle jet aka emulsion tube), jet needles.

The needle clip might need to sit in 4:th notch from top with pods and open exhaust.   3:rd (middle) is stock Honda CB750 (was on my K6)
Pilot 40, same with pods as well as air box, stock 736 or 836 + other mods giving 80rwhp
Main: Maybe 125 or more with pods and open exhaust. I'm not surprised about 140 ...
Then give the carbs a good clean. Some corrosion need vinegar bath for an hour, not more and carfeully rinse them, carbs as well as the removed jets their bleeder holes clogged by corrosion and old fuel + air screws.

[ekpent]

 Don't be intimidated about the old 750 round top carbs. They are the easiest ones to deal with around, very simple and super easy to work on.I also would be cracking them open to make sure the slow jets are clean and clear,the mains are screwed in and that the needle jet spring tips are not froze up. Also be nice to know for sure what size jets you have. Once you know all is good you can move on to other issues if you still have them.

[Blue2swing]

Thanks guys, I do have some reading material on the CB750 carbs that I purchased when I first started the build but never got around to reading. I'll crack that open to familiarize myself with the carb functions and how to adjust them. I'll try the K&N pods when they come in and if that doesn't help then I'll crack the carbs open to check the needles and do some internal cleaning and adjustments.

All great information I've been receiving and greatly appreciated!! I'll also check the D7ES plugs with the info on the link to make sure they are not copies. I didn't look at the price for regular D7ES's. I just clicked purchas and thought nothing of it. Wouldn't be surprised if they where counterfeits .

[Yamahawk]

I also checked my DR8ES-L plugs off eBay, and they appear genuine... good thing to know about the counterfeit plugs though!
Charlie

[BPellerine]

you say it ran well with the stock airbox,if you still have it try running the bike with it and note any change.bill

[Blue2swing]

you say it ran well with the stock airbox,if you still have it try running the bike with it and note any change.bill

Bill, you're a genius . Thank you! I feel kind of dumb for not having thought of that, lol. I'm won't have time to work on the bike till Monday which happens to be the same day the K&N Pods arrive. I'll do a couple of test then. Plan will be to pull and clean the plugs before each run. First run will be the current cheap pods that I believe are giving me the trouble, test 2 will be the stock air box, test 3 will be the K&N pods that claim to resolve problems like this with no need to adjust the carbs if all is working ok before the change. The air box test Bill suggested will give a good idea if all is working ok with the mostly stock set up befor trying the K&N's.