Running on 1.5 cylinders

mbrick

mbrick

Location
Los Gatos, CA
Yes! I buy them from Rockauto.

The BR8HS 6715 are $2.11/ea but come in a 10 pack. https://www.rockauto.com/en/parts/ngk,6715,spark+plug,7212
The BR8ES 3961 are $1.42/ea (what a steal) and $3 to ship 4 of them. https://www.rockauto.com/en/parts/ngk,3961,spark+plug,7212
The non-solid top B7HS 5110 are also $1.42/ea.
The non-solid top BR7HS 4122 are $1.29/ea.
You can usually find a current promo code if you google it.

This eBay seller has the B7HS for $2.21/ea shipped which is also pretty good. https://www.ebay.com/itm/152422608859
 
Freakrider

Freakrider

X247
Location
Tampa Bay area
mbrick said:
Yes! I buy them from Rockauto.

The BR8HS 6715 are $2.11/ea but come in a 10 pack. https://www.rockauto.com/en/parts/ngk,6715,spark+plug,7212
The BR8ES 3961 are $1.42/ea (what a steal) and $3 to ship 4 of them. https://www.rockauto.com/en/parts/ngk,3961,spark+plug,7212
The non-solid top B7HS 5110 are also $1.42/ea.
The non-solid top BR7HS 4122 are $1.29/ea.
You can usually find a current promo code if you google it.

This eBay seller has the B7HS for $2.21/ea shipped which is also pretty good. https://www.ebay.com/itm/152422608859
Click to expand...
Thanks just ordered a 4 pack of BR8ES where do they ship from ?
 
mbrick

mbrick

Location
Los Gatos, CA
Nice, glad I could help out.

They have a few different regional warehouses so you would have to ask them to know. I always receive orders within a few days though. I sometimes add on some oil filters, etc that I probably need. You just have to check if everything is coming from the same warehouse (shows on the cart page) otherwise wait on the extra parts because the shipping cost is per warehouse.
 
SuperJet-Dave

SuperJet-Dave

Location
Rochester, NY
With the replacement reeds/manifold it seems to run slightly better, but still not right. Still can run almost the same with the rear spark plug removed. It barely can start when the front spark plug is pulled (use a third plug in the hole, with the removed plug still in the boot and grounded... want to keep the coil from being damaged).
Compression test is similar... 160 psi in the front, 150 in the back. Again not ideal (should be higher with the protec head, and should be closer to each other, but still within 10%) but should not be problematic. Both exhaust exit ports feel similarly hot. Occasionally smoke will come out of the rear/suspect cylinder when removing the spark plug, but not more often then not it does not.
Any other suggestions out there?
 
mbrick

mbrick

Location
Los Gatos, CA
Are you talking about the hard to start or? You first talked about one cylinder running intermittently but later said it won't start.

A dirty carb (jets, idle circuit, etc), poor performing pump or poor performing diaphragm can make it hard to start.

What is the idle RPM? Sometimes a bit more idle will also help with starting.

You'd have to move the ebox but maybe try switching the plug wires to confirm there is not an issue with the coil/wire causing that one cylinder to have issues. Will help isolate if it is spark or carburetor or mechanical.
 
SuperJet-Dave

SuperJet-Dave

Location
Rochester, NY
mbrick said:
Are you talking about the hard to start or? You first talked about one cylinder running intermittently but later said it won't start.

A dirty carb (jets, idle circuit, etc), poor performing pump or poor performing diaphragm can make it hard to start.

What is the idle RPM? Sometimes a bit more idle will also help with starting.

You'd have to move the ebox but maybe try switching the plug wires to confirm there is not an issue with the coil/wire causing that one cylinder to have issues. Will help isolate if it is spark or carburetor or mechanical.
Click to expand...

No problems with starting.
When I pulled the spark plug from the good cylinder and only have a spark plug in the suspect cylinder it is hard to start. (Other way around is no problem).
Have new spark plug wires & boots (JSS). Tried switching plug wires and problem does not change. New CDI as well. Tried coil and wires from other Superjet, no change.
Thanks
 
mbrick

mbrick

Location
Los Gatos, CA
Apologies, I was mixing it up with another thread I was just reading that evolved into hard to start.

If you tried swapping the wires you know the coil is not the issue, so it is either the carb or mechanical on that cylinder. And you tried another coil and wires, and new plugs to doubly rule it out.

It's really taking a simple approach but if you have access to another SJ, can you borrow those carbs for a few min?

Tank vent is OK?
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
SuperJet-Dave said:
I have rebuilt the carbs (using Mikuni rebuild kits) and have taken them apart and cleaned for good measure. What is the thinking on this? That restricted (or too much) fuel or air could cause the cylinder to underperform??
Click to expand...
You got one cylinder that is working fine. You have another that is not working fine. Either you have a bad carb that is not sending fuel. or you have an issue with that cylinder (Cracked sleeve, cracked cylinder itself, bad intake leak, bad leak at base gasket........) You got something going on.
 
SuperJet-Dave

SuperJet-Dave

Location
Rochester, NY
Big Kahuna said:
You got one cylinder that is working fine. You have another that is not working fine. Either you have a bad carb that is not sending fuel. or you have an issue with that cylinder (Cracked sleeve, cracked cylinder itself, bad intake leak, bad leak at base gasket........) You got something going on.
Click to expand...

Makes sense. Thanks
 
Req

Req

Location
SW Tenn
I have something similar that just started happening to me. Last ride out it was running great. Me and my son ran through most of the tank and then I topped it off and kept riding. Shortly after it started running like it only had half power. Water was flowing great out of the pissers, no premix smoke in the engine bay, temp sensor is disconnected, carbs were rebuilt at the start of the season and I run filters. I took it out this afternoon after I checked the compression, plugs, and swapped to fresh gas. Its still doing the same thing even though everything checked out. I took a video to demonstrate.

Throttle response is bad, its running rough and has less power than my sons 650sx (it normally runs amazing), and it labors up to 3/4 rpm and then taps out.


Does anyone have any ideas on where I should go next? Plug wires? Carbs?

Thanks

Edit: Tracked the issue down to a broken reed for me. Leaving the post up for troubleshooting purposes for future members.
 
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SuperJet-Dave

SuperJet-Dave

Location
Rochester, NY
mbrick said:
Apologies, I was mixing it up with another thread I was just reading that evolved into hard to start.

If you tried swapping the wires you know the coil is not the issue, so it is either the carb or mechanical on that cylinder. And you tried another coil and wires, and new plugs to doubly rule it out.

It's really taking a simple approach but if you have access to another SJ, can you borrow those carbs for a few min?

Tank vent is OK?
Click to expand...

Hmmm. Never thought of swapping the carbs from my other SJ. Simple enough to do, and should fully determine if carbs are the issue or not.

Have not checked tank valve. Again easy enough to do.

Thanks for the ideas
 
SuperJet-Dave

SuperJet-Dave

Location
Rochester, NY
orangefinger said:
primer line hooked up to on/reserve instead of return line......primer defective you are pulling air thru on/reserve line into carb....

just an idea
Click to expand...

Primer is T’ed into the reserve line (can see it in the picture. The primer line is yellow). The ON line was removed. The reserve line goes straight to the carbs. The return line goes back into the tank where the ON line normally is. I quickly tried removing the primer line at the T and covered it with my thumb. Did not seem to make much difference in running rough (bummed, I liked the idea) I may try a more thorough test tomorrow.
Air blows into the short line fine. The other hole (vent hole) is plugged. I bought the machine configured like this, so I am not sure this is a likely culprit.
d50876a6b72a3a5b1912cadfd71dee5e.jpg
 
SuperJet-Dave

SuperJet-Dave

Location
Rochester, NY
Removed the pro-tec head. There is some pitting on the front “good” cylinder dome. Rear “bad” dome looks ok. Both cylinder sleeves look ok. No damage that I can see. There is no head gasket, just some black RTV like stuff.
Do I need to look further? Any suggestions? Anything I am missing from the pictures?
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