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Discussion Starter · #1 · (Edited)
Hi Guys,

I am very new to this site, and new to having a cx500 1978. The CX500 I had got hold of was very worse for wear so we have taken the best bits and I’m currently in the process of using it in a tuk tuk. ( reason explained at the bottom)

I really could do with some help, and apologies if a lot of this is mentioned on the site but where we are completely using the engine in another vehicle I could do with some help.

Air filters - the air box has completely gone so we are looking to hear what filters you guys are using..

Exhaust - so out of the exhaust manifold we have had to perform a 180 degree tight bend. From there, we have no idea what to use on the back end of each pipe. We want ideally a pair of straight silencers, in car terms back boxes I guess. I did take a read up of calculating exhaust criteria and it blew my mind in all honesty. Any product suggestions would be great. Just a pair of straight 3in chrome round exhaust tails would be great, but obviously we want to keep some kind of performance, MPG and noise control.

Electrical - so we have had to cut the bike wiring loom back ( and also the tuk in places ) ( losing all indicators, lights etc ) and integrate to make one loom. I have spent days removing wires to keep it all clean, tidy and how it should be. On the CX500 loom, there is a small fuse box with some kind of diode in it. We are fused elsewhere so when I tried to remove it, the engine wouldn’t start. When put back in, starts lovely. Any idea what it actually does, and is it possible to remove it to tidy it up?

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The reason behind this crazy project is that I have done a few charity rallies around the world. I have completed a banger rally across Europe, taken a tuk tuk over the Himalayas and also a tuk tuk from south to northern India..

I am based in Chelmsford, Essex, uk, in June 2020 we are taking on the Baltic Sea circle rally, for MIND mental health charity. We have raised £4000 for this trip so far, but need to get this finished ?‍♂

Thanks in advance, we really appreciate the support and help.

cheers

Clarky
 

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'84 CX650E that is evolving into a GL500
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Sounds like a neat project.

We always recommend adding your location to your profile and your bike's model and model year (NOT year first registered like the UK paperwork will show) to your signature so that you don't have to remember to tell us every time and we don't have to ask when you forget.

For the exhaust, many of us have had good results using original Harley mufflers (people often have the dealers replace the mufflers before they take delivery of brand new HDs so you can often get the originals really cheap) but that might not fit what you are doing. Maybe something similar to VW beetle muffler might fit...

The diode in the fusebox is probably why it won't start. As you probably know, the starter motor is not supposed to be able to run when the engine is in gear unless you disengage the clutch (it will start if the clutch lever is pulled no matter what gear it is in). Two circuits are involved in that:
1) The starter disconnect switch (in the clutch perch) interrupts the starter solenoid circuit between the solenoid and ground, preventing it from being energized unless the clutch lever is pulled.
2) The neutral switch interrupts the neutral light circuit between the light and ground.

The diode is connected between the neutral light circuit and the starter solenoid circuit so that the neutral switch bypasses the starter disconnect switch but the starter disconnect switch has no effect on the neutral light. If the diode is missing or has failed in open circuit mode the starter will only operate when the clutch lever is pulled.

BTW: You can download the Factory Shop Manual and the colour wiring drawing from the CX Wiki (link in my signature).
 

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Discussion Starter · #3 ·
Thanks sidecar Bob, appreciate the comments! I have updated my signature ( I think ) so now it should show everyone what I am upto!

Thanks for the update on the exhaust, I’m going to check out eBay etc and see what is around. It’s a bloody minefield knowing what is compatible and what is not, in a dream world you would have one of everything and keep changing them until it sounds and fills good.. in reality.. never going to happen.

Thanks for summing up the electrical side of things, I will speak to my friend who is far more clever than me. I completely understand your explanation though! I guess in reality the system works really well. Cannot wait to properly take it for a test drive!

So if you are using HD mufflers, what air filters are using and also jets? If I had my way I would prob leave the Honda setup as it was.. but for obvious reasons I can’t. I’ve read jets being 90/120 and also k&n 54mm oval filters and now HD exhausts.. hoping this is going to run reliable and not set everyone’s car alarms off!!

Thank you for your very helpful response, appreciated!
 

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'84 CX650E that is evolving into a GL500
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From what I've been told HD mufflers are about as loud as the originals except that they are a bit more "throaty". FWIW, my non-biking neighbours have told me they like the way mine sounds.

I've always run the stock air cleaners on mine (with a home brew foam filter for the last few years) so even with the Harley mufflers I haven't needed to re-jet. There is lots of information on the forum about pod filters, both pro and con (aside from the jetting, apparently some of them block ports in the carb inlets).

If I was doing what you are I think I'd try to find an original airbox, if only so that it wouldn't have exposed filters inside the engine compartment. But that's just me and I'm sure others (Murray?) will have different ideas.
 

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Discussion Starter · #5 ·
I’m completely torn with the air filter situation to be honest. Honda designed it all for a reason and that’s why it’s one of the most reliable engines out there, yet 40 years on technology has changed.

I will read up on some of the threads, and a take a view. From your post, went on eBay, pair of HD mufflers that look great .. £55 delivered.. will be here by the weekend.. thanks so much for the tip!
 

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I can't say about UK prices but I wouldn't have paid that much here. I think I paid the local aftermarket Harley place about $10 CAD each for the last ones I bought but that was a few years ago so I will probably pay about $25-30 this year.
 

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the engine will pull better if you have a longer pipe than the tight bend you have plus a muffler short exhaust does not work as well
adding 500mm - 575 mm will help with torque and scavenging across the power band
you may want to rejet to 85/118 mains if you have any performance issues

when pulling that weight please make sure you put new clutch springs in the main clutch the springs in it are 35 plus year sold and weak

these will prevent a clutch change

if you cant fit a air box use a top quality pod filter keep it oil and as its in the engine compartment/ tire area you could put /pre fil;ter rain socks on them



 

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Discussion Starter · #8 ·
Sidecar Bob and murryf thank you so much for your help. I will looking into everything you have said. There is not much we can do about the 180 degree bend at the front at the moment.. it’s not ideal at all but we really do not have anywhere to go with it..


The sock over the air filter is a great idea thank you very much for the tip.
When you say 500 - 575mm of pipework, is that between the engine and the muffler? I think we will be slightly longer than that.

I have just ordered the clutch springs, I am really keen to try and do the best I can with this, eventually I want to complete the mongol rally so I want to try and listen to people in the know and do the best I can.

k&n 54mm oval pods turned up today. I managed to remove the temptation of buying cheap imitation looking filters after watching a YouTube comparison video. Some of the cheaper ones look absolutely shocking!

I really appreciate the comments by both of you, if you think of anything else let me know. I will keep posting updates in here of photos so you can watch the build! I’m a carpenter by trade, I have a few mechanical mates but I’m really enjoying getting involved and this forum is bloody awesome!

massive thanks to whoever manages it all.
Cheers Clarky.
 

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FWIW, my CX650E based sidecar outfit is my winter vehicle. I am watching this project with a touch of envy (I even paused while typing post #4 to do a quick search for used Tuks in this area :rolleyes:
 

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Discussion Starter · #10 ·
FWIW, my CX650E based sidecar outfit is my winter vehicle. I am watching this project with a touch of envy (I even paused while typing post #4 to do a quick search for used Tuks in this area :rolleyes:
Well if I can help in anyway then please do let me know. Always keen to give back any help and advice I can. With regard to the cx500 engine it is a bit one way traffic at the moment but im learning!

Mine is an Indian tuk tuk, you can get Thai tuks too.
 

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'84 CX650E that is evolving into a GL500
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Unfortunately, there are none available around here right now. Or perhaps that is fortunate because I already have enough projects &c to keep me busy for a long time....
 
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