Aftermarket Flame Arrestors Carb Rejetting Help

[RebuiltSeadooBaffles]

I picked up a 97 SPX 787 a couple weeks ago and its has a aftermarket R&D flame arrestor on it with stock carb jetting, the guy had the LSA out 2 full turns and the highs out 2 1/4 turns! (Motor ate bearings but pistons looked good). Questions is should I up the jetting? If so what do I need to buy, pretty sure I have 1.5 N/S btut do not know how to tell.

 

[Dr Honda]

Generally... a less restrictive air box, is better served by lowing the pop-off.

Personally... I would get a stock air box, and bolt it back on, if this is a recreation ski. The OEM air box, is not a restriction... so the aftermarket system won't add power to a stock engine.

Besides... the OEM box keeps the engine safer from water ingestion.


OK... with that said... I'd put the low needle back to the stock setting... open the highs 1/4 turn more... and lower the pop-off 10%. (or just to the low, stock spec) Then... tune from there.

 

[RebuiltSeadooBaffles]

Thanks Dr. Honda, I have pop off on both carbs at 27-28 (think thats good enough?), I cannot lower the pop off anymore than that as the tabs are bent up to their limit. I do not want to spend $50 on a airbox so if I can get this to work without re-jetting I will be happy, FYI it is a R&D FA on it. If this in ANY WAY has a chance of running lean due to not re-jetting I do not want these, I have a new motor coming and do not want to risk it!

 

[Dr Honda]

Thanks Dr. Honda, I have pop off on both carbs at 27-28 (think thats good enough?), I cannot lower the pop off anymore than that as the tabs are bent up to their limit.

If they are bent up more that 1mm... then that can cause the engine to run lean, since you are restricting the needle and diaphragm movement. Personally... I would change the springs to achieve the desired pop-off.

I do not want to spend $50 on a airbox so if I can get this to work without re-jetting I will be happy, FYI it is a R&D FA on it. If this in ANY WAY has a chance of running lean due to not re-jetting I do not want these, I have a new motor coming and do not want to risk it!

Yes... it will run lean without proper tuning. If you make a change to a high output engine... you have to tune. So... you can't just make a few quick "Tweaks" and hope for the best. You will need to go out with a few sets of fresh plugs, and probably pull the carbs a few times... and you will want a few other jets, and regulator springs.


This is why I suggest going stock. It sounds like you really don't want to mess with it, and we all know they will run perfect at all the factory specs. Besides... I bet you can find a stock 800 airbox for the price of the shipping... and you can sell the aftermarket unit. When it's all said and done... you will have the reliability you want, and you will turn a profit.

 

[RebuiltSeadooBaffles]

In the market for a stock airbox....