Project 3LN1 Restoration

Well ****, another hurdle, lucky I took off the front wheel. Turns out the crash was worse than just breaking a fairing. Cracked front fork, now I’m worried there’s other damage. Going to need to strip down the whole thing now.


I’m buying another 3LN1 for $450, non runner, should be able to get some parts off it and hopefully swap the front fork on.

Sorry if this is a vague question but to ease my mind and make sure I don’t miss anything what should I really check over now. Must have been a substantial hit to crack it like that. Would the steering head in the triple clamp be bent. Cheers.

 

Hey guys, sorry for the extremely late response, I haven't been active for a while, fully bogged down in Uni work, the semester is nearly over though so it will be full steam ahead on the resto soon. My litetek seal kit has fully arrived and I almost have everything I need. Good to hear its not crash damage, that would be legendary if I could grab those lowers off you @ruckusman . There is some pitting on my fork uppers but its not where they travel to I don't think, will need to send some pics when i get time and also check if they are straight. Thanks again.

 

No worries @ruckusman. There’s no rush, my last exam is 1st of July and then it’s full steam ahead on the restoration. Hopefully by then you’ll be back. I’ll check if the forks are straight soon and will make sure the missus doesn’t see any dirt on the bench hahaha. I took the steering head off and the bearings seem pretty old. If anyone has the specs for them that would be helpful so I can grab some new ones, otherwise, I’ll try figure out an equivalent from the parts manual or see if Yamaha has the original part. Once again, appreciate your incredible help throughout this, I wouldn’t have been able to do it without you. The first ride is approaching ever so soon and I’m excited.

 

Hey guys managed to get the brakes finished and took it for a test ride today. Has had some issues. The fuel levels are all set properly and the jets, needles and needle positions are all correct. The inside of the carbs are also clean.

Firstly, the bike hasn’t been registered since 2005 and it has only ever revved in neutral while testing. It can comfortably hit 18k rpm in neutral and it sounds great. Although there is a bit of fuel smell. Initially, it would stall when put into gear. After a while I assume the clutch freed and it could engage nicely because I took off and rode it around my street. It stalled a few times under load and failed to idle. I set the idle quite knob high and this fixed the issue and I was able to get into second gear however the bike didn’t really want to go past 10-15k and it surged quite badly. Like it would give power and then have none and then power again and then none. I wasn’t going very fast or far from my street (no rego) but at some points it had no surging and rode fine but still seemed to have a a lower rev limit. It also went up the extremely steep hills in my area fine.

I have a few suspicions.
Firstly my fuel lines are quite long and tangled as I had the tank out of the bike for testing before. Secondly, after stalling or loosing power the pump will prime for a while as if it’s filling the carbs when you turn on and off the switch. So maybe the carbs aren’t getting filled at a high enough rate(tubing or pump)

I will also need to check the fuel level and float heights again so I’m 100% sure.

Also, I turned the mixture screw 3 turns out I’m pretty sure. The bike varies idle speed a lot while idling. Sometimes it seems like it’s chugging and then with a rev it will stop and sit at 6k rpm consistently.

The needles also didn’t seem worn but it’s impossible to check the emulsion tubes. Maybe they are worn.

What should I do @ruckusman @GreyImport @my67xr

 

I put new plugs when I refreshed all the engine fluids and rebuilt the carbs. Maybe the coils are weak/having an issue but it sounds like it’s definitely running on 4 cylinders. I have a suspicion it’s because I haven’t put the air box on yet nor have I tightened the carbs into the boots that go on the intake manifold so maybe some air is slipping past. I’ll test that in the next few days and see. I ran out of battery down the road so the bike is in my mates front yard for now haha.

 

Thanks so much Blair, I haven’t done this yet. This is likely the issue. Although does it also explain the surging? Or might that be due to a combination of no airbox and air cleaner and the carbs not being screwed tight to the intake boots. I guess I’ll try tomorrow and find out.

Also how do I sync the carbs. I understand the guide you sent but how do you sync the butterfly position ?

Also, does the fact that they are 3LN3 carbies matter on a 3LN1 engine or are all the engines the same?

@maelstrom

 

Guys I’m at my wits end, I spent all day ******* around and I feel like I have gone 30 steps backwards now.

I tightened the carbs properly to the boots and installed the air box and air filter properly.

I swapped the fuel pump over and this new one is much nicer and actually pumps a consistent flow rather than spluttering air and fuel like the other one (I didnt realise that wasn’t normal ).

I tried to bench sync the carbs using a needle as a feeler gauge and got them all in sync as close as possible before I get a manometer to get them perfect.

After putting them back on the bike sounds like **** now and is burbly with the occasional pop. Furthermore it can barely even idle now and won’t rev at all. There is smoke coming back through cylinder 1 when taking off the airbox cover to check and it just doesn’t work.

It is incredibly frustrating that I went from an almost working bike that could rev all the way up and work fine (other than the surging, likely air leak and fuel pump) to one that barely works at all now.

I wish I never bench synced it and just installed airbox and new fuel filter and tested first as that’s all I have changed for the carby to have this issue now.

Is it also possible that something in the engine is now broken.

sorry for the long message and thanks again

@ruckusman @beano @maelstrom @my67xr
@GreyImport

@Murdo