Seca turbo without turbo

Hi all, I have built a naked turbo and had enough parts to build another . The bike without the turbo runs great up to 5000 rpm then bogs and misses , this is close to when the turbo would come in ie 6000 rpm I am guessing I need to vent the carbs ? any theories cheers

 

That's sad. These low compression motors need that boost to feel good IMO.

Do you still have the turbo pressure box or ignition box connected. My guess is it's looking for boost and when it's not seeing it,something weird is happening with ignition.

 

Hi I agree its sad my other turbo works perfect its just I had enough spares to build another bike ( instead of leaving them on the spares shelf ) I have all the ignition as standard I have tried both with and without the boost sensor connected and I have completely swopped ignition boost sensor and knock sensor from the other bike

 

Now you've peaked my interest. As another who is in process of building my own naked turbo I'd really like to see pics of your bikes.

I'm not sure if Crank was referring to the pressure sensor or the surge tank?
What are you running on this bike upstream of the carbs? Running good to 5,000 then bogs and misses is symptom of pod filters.

 

Well both I guess. If the surge tank was still there and was being used as a make shift airbox that might be better than the open pods. I would just work my way backwards now that there is no boost, there is less air and less fuel needed. Are you still using the electric fuel pump and FPR?

 

Hi, thanks for the replys, I am not running the pump I see your point about pods as I am running open carbs, I do have the surge tank however I can't try it yet as two chokes are not working so I have to choke with my hand once started it runs perfect to 5k plugs a nice grey/brown I will sort the chokes this weekend and post the results with the air filter on. Here's some pics chrome one turbo black not . cheers guys looking forward to comments good or bad

 

Here's a few more pics

 

Impressive work, worthy of much more discussion

 

Thanks Simmy I will be glad to discuss them more. Fixed the chokes so I can try it with the air filter next.

 

Good looking bikes! I prefer the black paint to chrome. What tank is that? Is it the same tank on both?

 

Thanks, they are benelli Mojave tanks you can get them on eBay from India. I prefer the black too but they needed to be different. If you are running a turbo you will need the twin petrol tap version ie pump feed and return air tool adaptors thread straight in, the downside is no reserve

 

Looks pretty good. I'd love to hear the turbo with that pipe on it.

 

Hi I will post a video if I can. Update I have fitted the airbox and filter with the turbo return pipe blocked off and it runs worse won't rev above 4k remove the filter and it goes to nearly 4.5k plugs sooty black , open carbs 5.5 k plugs grey/brown. My conclusion is that the turbo provides air even before boost ? Next move fit a turbo which I have but I will have to rob the pump from the other one. Anyone know of a car pump that might work bearing in mind I am in the UK . Have a good one

 

According to Yamaha they incorporated the reed valve arrangement to bypass the turbo until pressure goes positive because turbos typically restrict the air when not on boost.

Here is a fuel pump which I saw recommended on the TMIOA forum which I am also considering.

http://walbrofuelpumps.com/walbro-gsl395-fuel-pump.html

 

Cheers, I used the reed valve, guess I won't know for sure until I fit the turbo. Thanks for the info on the pump I think I will try my other first were its fitted its easily swopped then when its running good buy another pump

 

Yes I noticed you relocated the pump to the side of the bike. I suspect you found the stock pump mounts interfered with your new tank which I've discovered with my own project, I'm still hoping there is room there, just a few mm's lower.

I'm curious how stock your electronics are? Was there any difficulties eliminating the big Atari dash computer?

 

I located the pump there so it primed itself as my tank outlet is now lower than standard it would fit under the tank by removing the frame bracket . Removing the computer is easy most wires are self explanatory indicators etc or just not needed like boost gauge battery condition etc. The ones to watch are the headlight ones as they are routed through the computer and most important tacho wire orange if you get a cheap tacho it will blow the TDI unit I know I did it that's why the chrome one has a £200 kozo unit and the black has a tacho from a standard xj 650 and a £10 eBay Chinese one which works just as good. Best to deal with one wire at a time. Also you will need to relocate the tilt switch mine is under the seat now as are all the relays. As regards my black one just looked at the air box and read valve and it looks like it gets air from both inlets ie direct and turbo until it gets positive pressure and the read closes ( probably wrong ) but just gonna try without the read valve .

 

Forgot to say loads of the wires are for the self canceling indicators and just not needed best to rewire them from scratch using a standard indicator switch or the right ones will work and the left not. Other wires are obvious neutral night beam etc

 

If it's "crapping" at 5500-6000rpm and not building boost, chances are, boost is exceeding fuel pressure. You NEED a fuel pump producing more pressure than the turbo produces boost.

jeff

 

LOL Jeff, you need to read the entire thread as there is discussion underway of 2 bikes, one with a turbo and another as the subject outlines 'seca turbo without turbo'
The one crapping out in the mid-range is the bike without turbo and running (at the moment) open carbs.

 

could be a symptom of

 

Fitted the turbo no pump yet, ran great reved out and boosted until fuel starved , ordered pump sounds sorted. Just wanted to see if you could run one without a turbo unit seems not ?

 

Being that the bike ran better with less restrictive intake, I would guess that without the turbo to jam extra air into the engine at higher revs, you are simply running rich in the top end, I would try a rejet using a standard 650 as a base line, it should run fine without turbo.

 

Yes I think you are right, might as well leave the turbo on now, the reason I didn't want to was the tank but that's sorted now my mate has just welded the tap mounting from a turbo tank in for me cheers for the reply

 

I skimmed it Simmy....not enough I suppose.....lol

jeff

 

I like the add a turbo solution better than making it run well without it.

 

Hi all update so far fitted a pump and it ran great for a moment then flooded the engine . changed oil carbs are off again going to rig up with pump on the bench . reluctant to try parts from the other turbo as it runs perfect and don't want to disturb it. Picked up a 750 seca engine and carbs with a strange engine number ( best start another thread on that one )

 

When you say you fitted a pump do you mean a factory fuel pump? Also is your fuel pressure regulator in good shape?

 

Hi the pump is non standard but I have found one carb flooding going to leave it a couple of weeks now then sort the carb and take it from there thanks